Hotspot: Official change to Sun Studio 12 compilers on Solaris

This is the change request to make the SS12 compilers the official and default compiler to be used in jdk7 hotspot.

This change should include:
  1. Makefile change to not warn about SS12 usage (make it the default compiler)
  2. JPRT changes (make/jprt.* files) to make SS12 the default compiler.
  3. Updates to any README files in Hotspot that relate to compiler usage.

Before this change is done, we need complete testing of a full jdk7 built with SS12, and performance runs with alacrity to verify that we accept and identify any regressions this change might create. Major problems in testing or performance could delay this official change, and accepting any regressions may need to be done by some official body, who knows?