[Attribute/Diagnostics] Print macro if definition is an attribute declaration

[Attribute/Diagnostics] Print macro if definition is an attribute declaration

If an address_space attribute is defined in a macro, print the macro instead
when diagnosing a warning or error for incompatible pointers with different
address_spaces.

We allow this for all attributes (not just address_space), and for multiple
attributes declared in the same macro.

Differential Revision: https://reviews.llvm.org/D51329

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@359826 91177308-0d34-0410-b5e6-96231b3b80d8