thorough tests.
Original commit message:
[modules] Fix macro hiding bug exposed if:
* A submodule of module A is imported into module B
* Another submodule of module A that is not imported into B exports a macro
* Some submodule of module B also exports a definition of the macro, and
happens to be the first submodule of B that imports module A.
In this case, we would incorrectly determine that A's macro redefines B's
macro, and so we don't need to re-export B's macro at all.
This happens with the 'assert' macro in an LLVM self-host. =(
llvm-svn: 213416
Richard Smith