RFR(XS): 8245850: Obsolete UseLWPSynchronization

[Mikael Vidstedt]

Please review this small change which obsoletes the UseLWPSynchronization flag:

JBS: https://bugs.openjdk.java.net/browse/JDK-8245850
webrev: http://cr.openjdk.java.net/~mikael/webrevs/8245850/webrev.00/open/webrev/
CSR: https://bugs.openjdk.java.net/browse/JDK-8245851

Background (from JBS):

With Solaris removed (JDK-8241787) the UseLWPSynchronization flag no longer has any effect and should be removed using the normal process. Since the flag was really only useful on Solaris and since all the code it once controlled is now gone the flag will go directly to obsolete, skipping the deprecation step.

Testing:

* Manual verification running with the flag: spits out the warning as expected
* tier1: passes

Cheers,
Mikael