Move LangStandard*, InputKind::Language to Basic

This patch is a prerequisite for using LangStandard from Driver in
https://reviews.llvm.org/D64793.

It moves LangStandard* and InputKind::Language to Basic.  It is mostly
mechanical, with only a few changes of note:

- enum Language has been changed into enum class Language : uint8_t to
  avoid a clash between OpenCL in enum Language and OpenCL in enum
  LangFeatures and not to increase the size of class InputKind.

- Now that getLangStandardForName, which is currently unused, also checks
  both canonical and alias names, I've introduced a helper getLangKind
  which factors out a code pattern already used 3 times.

The patch has been tested on x86_64-pc-solaris2.11, sparcv9-sun-solaris2.11,
and x86_64-pc-linux-gnu.

There's a companion patch for lldb which uses LangStandard.h
(https://reviews.llvm.org/D65717).

While polly includes isl which in turn uses InputKind::C, that part of the
code isn't even built inside the llvm tree.  I've posted a patch to allow
for both InputKind::C and Language::C upstream
(https://groups.google.com/forum/#!topic/isl-development/6oEvNWOSQFE).

Differential Revision: https://reviews.llvm.org/D65562

llvm-svn: 367864
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 8ca866e..59662f8 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -15,6 +15,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclGroup.h"
 #include "clang/Basic/FileManager.h"
+#include "clang/Basic/LangStandard.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/BackendUtil.h"
@@ -1014,7 +1015,7 @@
 
 void CodeGenAction::ExecuteAction() {
   // If this is an IR file, we have to treat it specially.
-  if (getCurrentFileKind().getLanguage() == InputKind::LLVM_IR) {
+  if (getCurrentFileKind().getLanguage() == Language::LLVM_IR) {
     BackendAction BA = static_cast<BackendAction>(Act);
     CompilerInstance &CI = getCompilerInstance();
     std::unique_ptr<raw_pwrite_stream> OS =