[Bug c/49975] warn on malformed __attribute((...))__

[ext at sidvind dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49975

--- Comment #2 from David Sveningsson <ext at sidvind dot com> 2011-08-04 13:33:21 UTC ---
Might be valid, but confusing. If whitespace were required after "))" it would
make more sense as it is clear that a global is created.

As the documentation states that __attribute__ is the keyword, I think a
warning would be appropriate even if it is retained for compatibility.