RFR (S): 8181787: Remove Solaris SPARC GCC code

[Erik Österlund]

Hi,

The only supported way of building OpenJDK on Solaris is via the studio 
compiler. However, there are unsupported code paths that are enabled 
only if _GNU_SOURCE is defined. This might be problematic for multiple 
reasons. Checking for _GNU_SOURCE does not check for GCC, it checks 
whether the standard library is the GNU standard library. Most 
importantly, the code has been bit rotting and e.g. the inline assembly 
for atomic seems to have flaws. Since we never test the correctness of 
these code paths, I propose to remove this unsupported code.

Bug: https://bugs.openjdk.java.net/browse/JDK-8181787

Webrev: http://cr.openjdk.java.net/~eosterlund/8181787/webrev.00/

Testing: JPRT

Will need a sponsor.

Thanks,
/Erik