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/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index 1bea322..14db878 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -9,6 +9,7 @@
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/Basic/FileManager.h"
+#include "clang/Basic/LangStandard.h"
 #include "clang/Frontend/ASTConsumers.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
@@ -832,19 +833,19 @@
 
 void PrintPreambleAction::ExecuteAction() {
   switch (getCurrentFileKind().getLanguage()) {
-  case InputKind::C:
-  case InputKind::CXX:
-  case InputKind::ObjC:
-  case InputKind::ObjCXX:
-  case InputKind::OpenCL:
-  case InputKind::CUDA:
-  case InputKind::HIP:
+  case Language::C:
+  case Language::CXX:
+  case Language::ObjC:
+  case Language::ObjCXX:
+  case Language::OpenCL:
+  case Language::CUDA:
+  case Language::HIP:
     break;
 
-  case InputKind::Unknown:
-  case InputKind::Asm:
-  case InputKind::LLVM_IR:
-  case InputKind::RenderScript:
+  case Language::Unknown:
+  case Language::Asm:
+  case Language::LLVM_IR:
+  case Language::RenderScript:
     // We can't do anything with these.
     return;
   }