Apply changes to migrate to LLVM Mar 6th 2011.

- API for name mangling. (Changing from non-public APIs to the
  public one)

- API changes for clang::Diagnostic::getNumErrors ->
  clang::Diagnostic::hasErrorOccurred

- API changes for clang::CharUnits and Quantity type.

- API changes libLLVMSystem -> libLLVMSupport.

- Change clang::Token::eom -> clang::Token::eod.

- Remove SourceRange parameter for DeclRefExpr::Create and
  MemberExpr::Create.

- Add const qualifier for several unsafe type cast.
diff --git a/slang_rs_export_element.cpp b/slang_rs_export_element.cpp
index 9887f0b..1ebc655 100644
--- a/slang_rs_export_element.cpp
+++ b/slang_rs_export_element.cpp
@@ -94,7 +94,7 @@
                                    "your macro)");
       RSExportVectorType *EVT =
           RSExportVectorType::Create(Context,
-                                     static_cast<clang::ExtVectorType*>(
+                                     static_cast<const clang::ExtVectorType*>(
                                          T->getCanonicalTypeInternal()
                                              .getTypePtr()),
                                      TypeName,