[8u20] Request for approval for bulk integration of hs25.20-b16

[John Coomes]

Requesting approval to integrate hs25.20-b16 into jdk8u20-b16.

A webrev is available at:

http://cr.openjdk.java.net/~jcoomes/8u/8u20/hs25.20-b16-jdk8u20-b16.webrev

Pre-integration testing is in progress; the integration will proceed
only after SQE has analyzed the results and approved.

The fixes in the proposed integration are below.  All have undergone
nightly testing and are already in a jdk9 repository except 8042949
and 8043308, neither of which are applicable to jdk9.

8022070: Compilation error in stubGenerator_sparc.cpp with some compilers
8032551: Remove UsePPCLWSYNC from globals.hpp
8037816: Fix for 8036122 breaks build with Xcode5/clang
8038212: Method::is_valid_method() check has performance regression impact for stackwalking
8041918: BootstrapMethods attribute cannot be empty.
8042059: Various fixes to linux/sparc
8042786: Proper fix for 8032566
8042949: +UnlockExperimentalVMOptions missed from TestUseRTMLockingOptionOnUnsupportedVM.java test
8043029: Change 8037816 breaks HS build with older GCC versions which don't support diagnostic pragmas
8043164: Format warning in traceStream.hpp
8043308: new hotspot build - hs25.20-b16