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.

applications/utilities/mesh/manipulation/setSet/setSet.C

@@ -55,10 +55,11 @@ Description
 
 #include <stdio.h>
 
-
-#ifdef HAS_READLINE
+#ifdef HAVE_LIBREADLINE
     #include <readline/readline.h>
     #include <readline/history.h>
+
+    static const char* historyFile = ".setSet";
 #endif
 
 using namespace Foam;
@@ -66,11 +67,6 @@ using namespace Foam;
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 
-#ifdef HAS_READLINE
-static const char* historyFile = ".setSet";
-#endif
-
-
 // Write set to VTK readable files
 void writeVTK
 (
@@ -790,7 +786,7 @@ int main(int argc, char *argv[])
     printAllSets(mesh, Info);
 
     // Read history if interactive
-    #ifdef HAS_READLINE
+    #ifdef HAVE_LIBREADLINE
     if (!batch && !read_history((runTime.path()/historyFile).c_str()))
     {
         Info<< "Successfully read history from " << historyFile << endl;
@@ -872,7 +868,7 @@ int main(int argc, char *argv[])
             }
             else
             {
-                #ifdef HAS_READLINE
+                #ifdef HAVE_LIBREADLINE
                 {
                     char* linePtr = readline("readline>");