RFR(S): 8158938: AIX: some more new hotspot build fixes

[Volker Simonis]

Hi,

can I please have a review for the following two (top-level and
hotspot) AIX-only changes:

http://cr.openjdk.java.net/~simonis/webrevs/2016/8158938_top/
http://cr.openjdk.java.net/~simonis/webrevs/2016/8158938_hs/
https://bugs.openjdk.java.net/browse/JDK-8158938

Although the changes are AIX only, they require the recreation of
generated_configure.sh in the top-level repo and touche a shared make
file in the hotspot repo, so I need a sponsor for both of them.
Ideally they should go into the same forest although they have no
dependencies on each other. It's not important for me into which
forest they will be pushed, as long as they eventually arrive in jdk9.

The changes in some more detail:

top-level repository:
- fix AIX build to set -DDONT_USE_PRECOMPILED_HEADERS
- don't build gtest on AIX by  default
- move optimization flags from JVM_CFLAGS to C_O_FLAG_HI* where they
really belong to.

hotspot repository:
- build jvmtiEnterTrace.cpp on a lower optimization level to prevent
excessive build times.

Thank you and best regards,
Volker