r194296 - Use rauw for all discardable aliases, not just linkonce_odr.

[Rafael Espíndola]

> How does the attached patch look?

Close, but please:

* Disallow only the "available_externally always_inline" combination.
Your patch would disable it for all always_inline.
* Add a comment to the file saying why we don't want to rauw if the
target is is available_externally always_inline and maybe a FIXME
about the existence of this combination being a bit odd.
* clang-format the test :-)
* merge the test into test/CodeGenCXX/ctor-dtor-alias.cpp

Cheers,
Rafael