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.

bin/tools/lib-dir

@@ -142,12 +142,18 @@ fi
 
 if [ -n "$resolved" ]
 then
-    case "$optSyntax" in
-    csh)
+    case "$optSyntax-$(uname -s 2>/dev/null)" in
+    make*)
+        printf "%s\n" "-L$resolved"
+        ;;
+    csh-Darwin*)
+        echo "setenv DYLD_LIBRARY_PATH $resolved:$DYLD_LIBRARY_PATH"
+        ;;
+    csh*)
         echo "setenv LD_LIBRARY_PATH $resolved:$LD_LIBRARY_PATH"
         ;;
-    make)
-        printf "%s\n" "-L$resolved"
+    sh-Darwin*)
+        echo "DYLD_LIBRARY_PATH=$resolved:$DYLD_LIBRARY_PATH"
         ;;
     *)
         echo "LD_LIBRARY_PATH=$resolved:$LD_LIBRARY_PATH"
@@ -155,7 +161,7 @@ then
     esac
     exit 0      # Good
 else
-    exit 1    # Error
+    exit 1      # Error
 fi