Newer Sun C compilers are not 'SUNwspro', but 'solstudio'.

(cherry picked from commit 78ab3d1a1e24336ae295c6766f0aa90bff964c53)
Sun c99 ccversion.

(cherry picked from commit 8f6660ae44158df9b0d94fc5d1c7deb9c85ea1ad)
Sun c99 doesn't like bare -O.

(cherry picked from commit a5a0b9b91da0e2ae65a3eaaed49632081d8eb2de)
Sun c99 needs -Xa for many system interfaces.

(cherry picked from commit 0b6032931d47da84e83a642fede2c6ebb0bcedeb)
Fix hint typo: No leading underscore in PERL_USE_SAFE_PUTENV

hints/solaris_2.sh generates a config.over script intended to add
PERL_USE_SAFE_PUTENV to ccflags, if it is not already present.  An extra
leading underscore in the check meant that the test always failed and
PERL_USE_SAFE_PUTENV always got added.

(cherry picked from commit dd25c352db6f2a0adb8324232f6ccfd456d603e9)