Fixes incorrect handling of the declaration context stack.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173250 91177308-0d34-0410-b5e6-96231b3b80d8
Fix regression in formatting pointer types.

We will need a more principled solution, but we should not leave this
unfixed until we come up with one.

Before: void f() { int * a; }
After:  void f() { int *a; }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173252 91177308-0d34-0410-b5e6-96231b3b80d8
Add a new LangOpt NativeHalfType. This option allows for native half/fp16
operations (as opposed to storage only half/fp16).

Also add some semantic checks for OpenCL half types.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173254 91177308-0d34-0410-b5e6-96231b3b80d8