Add frontend support for __vectorcall

Wire it through everywhere we have support for fastcall, essentially.

This allows us to parse the MSVC "14" CTP headers, but we will
miscompile them because LLVM doesn't support __vectorcall yet.

Reviewed By: Aaron Ballman

Differential Revision: http://reviews.llvm.org/D5808

llvm-svn: 220573
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 4060fab..8463138 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -837,6 +837,7 @@
           Tok.is(tok::kw___stdcall) ||
           Tok.is(tok::kw___fastcall) ||
           Tok.is(tok::kw___thiscall) ||
+          Tok.is(tok::kw___vectorcall) ||
           Tok.is(tok::kw___unaligned))
         return TPResult::True; // attributes indicate declaration
       TPResult TPR = TryParseDeclarator(mayBeAbstract, mayHaveIdentifier);
@@ -984,6 +985,7 @@
   case tok::kw___stdcall:
   case tok::kw___fastcall:
   case tok::kw___thiscall:
+  case tok::kw___vectorcall:
   case tok::kw___unaligned:
   case tok::kw___vector:
   case tok::kw___pixel:
@@ -1254,6 +1256,7 @@
   case tok::kw___stdcall:
   case tok::kw___fastcall:
   case tok::kw___thiscall:
+  case tok::kw___vectorcall:
   case tok::kw___w64:
   case tok::kw___sptr:
   case tok::kw___uptr: