XCore target: Add TypeString meta data to IR output.

This includes the addition of the virtual function:
	TargetCodeGenInfo::EmitTargetMD()

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207832 91177308-0d34-0410-b5e6-96231b3b80d8
XCore target: fix handling of -g0 flag

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207833 91177308-0d34-0410-b5e6-96231b3b80d8
XCore target: fix bug in dereferencing null pointer.

Also add basic cpp ABI tests where they differ from C ABI output.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207834 91177308-0d34-0410-b5e6-96231b3b80d8