Add ReportErrror/Warning to RSContext.

Remove a lot of boilerplate code by adding error reporting methods to RSContext.  There are still a few additional files that could be cleaned.  That will be for another CL someday.

Change-Id: I6a261735720227ac87d94dbdea5ce4a7b8ef6cca
diff --git a/slang_rs_export_foreach.h b/slang_rs_export_foreach.h
index 14266d5..a2f9a02 100644
--- a/slang_rs_export_foreach.h
+++ b/slang_rs_export_foreach.h
@@ -175,8 +175,7 @@
   static bool isGraphicsRootRSFunc(int targetAPI,
                                    const clang::FunctionDecl *FD);
 
-  static bool isRSForEachFunc(int targetAPI, 
-                              clang::DiagnosticsEngine *DiagEngine,
+  static bool isRSForEachFunc(int targetAPI, slang::RSContext *Context,
                               const clang::FunctionDecl *FD);
 
   inline static bool isSpecialRSFunc(int targetAPI,
@@ -186,7 +185,7 @@
   }
 
   static bool validateSpecialFuncDecl(int targetAPI,
-                                      clang::DiagnosticsEngine *DiagEngine,
+                                      slang::RSContext *Context,
                                       const clang::FunctionDecl *FD);
 };  // RSExportForEach