Incompatible change to macro behavior

[Roland McGrath]

The changes in commit 9f2e3c21f6506f081f1360f02b847606e0e00995 are an
incompatible change to existing macro semantics and break existing
code.
This makes GAS `.macro` incompatible with how it's always behaved
before, and incompatible with the Clang implementation.

This is not a minor change.  It's a fundamental change to the semantics.
It makes it impossible to define macro-defining macros, which was
possible before and has been used in the real world.

I don't see any alternative but to revert this change.