[Bug c/81824] Warn for missing attributes with function aliases

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81824

--- Comment #17 from Martin Sebor <msebor at gcc dot gnu.org> ---
Making -Wattribute-alias a synonym for -Wattribute-alias=1 makes sense.  I'll
take care of it.