Adding subjects to calling convention attributes. No functional changes intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195097 91177308-0d34-0410-b5e6-96231b3b80d8
Improving calling convention test coverage by adding tests for things not currently handled. Specifically: the diagnostics in SemaDeclAttr.cpp, and ensuring that calling convention attributes are applied to ObjC method declarations. No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195098 91177308-0d34-0410-b5e6-96231b3b80d8
Giving this test a triple since it uses a calling convention attribute.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195099 91177308-0d34-0410-b5e6-96231b3b80d8