ENH: Pass dependent library search path to linker on some platforms.

- Move runtime path ordering out of cmComputeLinkInformation
    into its own class cmOrderRuntimeDirectories.
  - Create an instance of cmOrderRuntimeDirectories for runtime
    path ordering and another instance for dependent library
    path ordering.
  - Replace CMAKE_DEPENDENT_SHARED_LIBRARY_MODE with explicit
    CMAKE_LINK_DEPENDENT_LIBRARY_FILES boolean.
  - Create CMAKE_LINK_DEPENDENT_LIBRARY_DIRS boolean.
  - Create variables to specify -rpath-link flags:
      CMAKE_SHARED_LIBRARY_RPATH_LINK_<LANG>_FLAG
      CMAKE_EXECUTABLE_RPATH_LINK_<LANG>_FLAG
  - Enable -rpath-link flag on Linux and QNX.
  - Documentation and error message updates

Source/cmExportBuildFileGenerator.cxx

@@ -122,7 +122,8 @@ cmExportBuildFileGenerator
 //----------------------------------------------------------------------------
 void
 cmExportBuildFileGenerator
-::ComplainAboutMissingTarget(cmTarget* target, const char* dep)
+::ComplainAboutMissingTarget(cmTarget* depender,
+                             cmTarget* dependee)
 {
   if(!this->ExportCommand || !this->ExportCommand->ErrorMessage.empty())
     {
@@ -130,13 +131,10 @@ cmExportBuildFileGenerator
     }
 
   cmOStringStream e;
-  e << "called with target \"" << target->GetName()
-    << "\" which links to target \"" << dep
+  e << "called with target \"" << depender->GetName()
+    << "\" which requires target \"" << dependee->GetName()
     << "\" that is not in the export list.\n"
-    << "If the link dependency is not part of the public interface "
-    << "consider setting the LINK_INTERFACE_LIBRARIES property on \""
-    << target->GetName() << "\".  Otherwise add it to the export list.  "
-    << "If the link dependency is not easy to reference in this call, "
+    << "If the required target is not easy to reference in this call, "
     << "consider using the APPEND option with multiple separate calls.";
   this->ExportCommand->ErrorMessage = e.str();
 }