extern C fixes

Source/cmCPluginAPI.cxx

@@ -22,6 +22,9 @@
 #include "cmMakefile.h"
 #include "cmCPluginAPI.h"
 
+extern "C" 
+{
+  
 void *cmGetClientData(void *info)
 {
   return ((cmLoadedCommandInfo *)info)->ClientData;
@@ -453,6 +456,8 @@ void cmRemoveFile(const char *name)
   cmSystemTools::RemoveFile(name);
 }
 
+} // close the extern "C" scope
+
 cmCAPI cmStaticCAPI =
 {
   cmGetClientData,