ENH: improve handling of ThirdParty packages

- generalize some of the library extensions (.so vs .dylib).
  Provide as wmake 'sysFunctions'

- added note about unsupported/incomplete system support

- centralize detection of ThirdParty packages into wmake/ subdirectory
  by providing a series of scripts in the spirit of GNU autoconfig.
  For example,

      have_boost, have_readline, have_scotch, ...

  Each of the `have_<package>` scripts will generally provide the
  following type of functions:

      have_<package>          # detection
      no_<package>            # reset
      echo_<package>          # echoing

  and the following type of variables:

      HAVE_<package>          # unset or 'true'
      <package>_ARCH_PATH     # root for <package>
      <package>_INC_DIR       # include directory for <package>
      <package>_LIB_DIR       # library directory for <package>

  This simplifies the calling scripts:

      if have_metis
      then
          wmake metisDecomp
      fi

  As well as reducing clutter in the corresponding Make/options:

      EXE_INC = \
          -I$(METIS_INC_DIR) \
          -I../decompositionMethods/lnInclude

      LIB_LIBS = \
          -L$(METIS_LIB_DIR) -lmetis

  Any additional modifications (platform-specific or for an external build
  system) can now be made centrally.

wmake/scripts/have_scotch

@@ -0,0 +1,174 @@
+#----------------------------------*-sh-*--------------------------------------
+# =========                 |
+# \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+#  \\    /   O peration     |
+#   \\  /    A nd           | Copyright (C) 2018 OpenCFD Ltd.
+#    \\/     M anipulation  |
+#------------------------------------------------------------------------------
+# License
+#     This file is part of OpenFOAM, licensed under GNU General Public License
+#     <http://www.gnu.org/licenses/>.
+#
+# Script
+#     have_scotch
+#
+# Description
+#     Detection/setup of scotch
+#
+# Requires
+#     config.sh/scotch
+#
+# Functions provided
+#     have_scotch, no_scotch, echo_scotch
+#
+# Variables set on success
+#     HAVE_SCOTCH
+#     SCOTCH_ARCH_PATH
+#     SCOTCH_INC_DIR
+#     SCOTCH_LIB_DIR
+#
+#------------------------------------------------------------------------------
+. $WM_PROJECT_DIR/wmake/scripts/sysFunctions # General system functions
+
+#------------------------------------------------------------------------------
+
+# Reset variables
+no_scotch()
+{
+    unset HAVE_SCOTCH SCOTCH_ARCH_PATH SCOTCH_INC_DIR SCOTCH_LIB_DIR
+    unset SCOTCH_VERSION
+    return 0
+}
+
+
+# Report
+echo_scotch()
+{
+    echo "scotch=${HAVE_SCOTCH:-false}"
+    echo "root=$SCOTCH_ARCH_PATH"
+    echo "include=$SCOTCH_INC_DIR"
+    echo "library=$SCOTCH_LIB_DIR"
+}
+
+
+# On success, return 0 and export variables
+# -> HAVE_SCOTCH, SCOTCH_ARCH_PATH, SCOTCH_INC_DIR, SCOTCH_LIB_DIR
+have_scotch()
+{
+    local header library static label settings warn
+    warn="==> skip scotch"
+
+    # Basic setup/checks
+    settings=$($WM_PROJECT_DIR/bin/foamEtcFile config.sh/scotch) || {
+        [ -n "$warn" ] && echo "$warn (no config.sh/scotch settings)"
+        return 1
+    }
+    . $settings
+    if isNone "$SCOTCH_ARCH_PATH"
+    then
+        [ -n "$warn" ] && echo "$warn (not available)"
+        return 1
+    fi
+
+
+    # Header/library names
+    header="scotch.h"
+    library="libscotch$extLibso"
+    static="libscotch$extLiba"
+
+
+    if hasAbsdir "$SCOTCH_ARCH_PATH"
+    then
+        header=$(findFirstFile $SCOTCH_ARCH_PATH/include/$header)
+
+        # FOAM_EXT_LIBBIN is allowed to be unset
+        library=$(findFirstFile \
+            $FOAM_EXT_LIBBIN/$library \
+            $SCOTCH_ARCH_PATH/lib/$static \
+            $SCOTCH_ARCH_PATH/lib/$library \
+            $SCOTCH_ARCH_PATH/lib$WM_COMPILER_LIB_ARCH/$static \
+            $SCOTCH_ARCH_PATH/lib$WM_COMPILER_LIB_ARCH/$library \
+        )
+    elif isSystem "$SCOTCH_ARCH_PATH"
+    then
+        header=$(findFirstFile /usr/include/$header /usr/include/scotch/$header)
+
+        library=$(findFirstFile \
+            /usr/lib/$library \
+            /usr/lib$WM_COMPILER_LIB_ARCH/$library \
+        )
+    else
+        unset header library
+    fi
+
+
+    # Header found?
+    [ -n "$header" ] || {
+        [ -n "$warn" ] && echo "$warn (no header)"
+        return 2
+    }
+
+    # Library found?
+    [ -n "$library" ] || {
+        [ -n "$warn" ] && echo "$warn (missing library)"
+        return 2
+    }
+
+
+    # Ensure consistent sizes between OpenFOAM and scotch header
+    # extract 'typedef int64_t SCOTCH_Num' or equivalent
+    label=$(sed -ne \
+        's/^.*typedef *\([^ ]*\) *SCOTCH_Num.*/\1/ip' \
+        "$header")
+    : ${label:=unknown} # Failsafe value
+
+
+    # No SCOTCH_VERSION set? Try to obtain from header
+    # extract #define SCOTCH_VERSION, SCOTCH_RELEASE, SCOTCH_PATCHLEVEL
+    [ -n "$SCOTCH_VERSION" ] || \
+    SCOTCH_VERSION=$(
+        eval $(
+            sed -ne \
+            's/^ *#define *SCOTCH_\(VERSION\|RELEASE\|PATCHLEVEL\) *\([0-9][0-9]*\).*$/\1=\2/p' \
+            "$header"
+        )
+
+        set -- $VERSION $RELEASE $PATCHLEVEL
+        IFS="."
+        [ "$#" -gt 0 ] && echo "scotch-$*"
+    )
+    : ${SCOTCH_VERSION:=scotch} # Failsafe value
+
+
+    case "$WM_LABEL_SIZE:$label" in
+    (32:int32_t | 32:int | 64:int64_t | 64:long)
+        echo "Scotch (label=$label) - $SCOTCH_ARCH_PATH"
+        export HAVE_SCOTCH=true
+        export SCOTCH_ARCH_PATH SCOTCH_VERSION
+        export SCOTCH_INC_DIR="${header%/*}"     # Basename
+        export SCOTCH_LIB_DIR="${library%/*}"    # Basename
+        ;;
+
+    *)
+        if [ -n "$warn" ]
+        then
+            echo "$warn (label='$WM_LABEL_SIZE', scotch.h has '$label')"
+        fi
+        no_scotch
+        return 1
+        ;;
+    esac
+}
+
+
+# Force reset of old variables
+no_scotch
+
+# Testing
+if [ "$1" = "-test" ]
+then
+    have_scotch
+    echo_scotch
+fi
+
+#------------------------------------------------------------------------------