[MS ABI] Error instead of generating bad vftables for certain virtual hierarchies (PR18967)

Erroring out until we fix the bug means we don't have to keep chasing down
this same miscompile in a bunch of different places.

Differential Revision: http://llvm-reviews.chandlerc.com/D2890

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202331 91177308-0d34-0410-b5e6-96231b3b80d8
Pass down the debug emission kind into the compile unit for code
generation purposes.
Paired with a commit to llvm.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202334 91177308-0d34-0410-b5e6-96231b3b80d8
Add category test case for attribute 'objc_protocol_requires_explicit_implementation'.

This test also illustrates that checking for properties is not working properly with
this attribute, as we are missing a diagnostic for a property not being implemented.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@202335 91177308-0d34-0410-b5e6-96231b3b80d8