RFR (M/L): JDK-8035400: Move G1ParScanThreadState into its own files

[Thomas Schatzl]

Hi all,

  can I have reviews for the above change? It moves G1ParScanThreadState
into G1ParScanThreadState*pp files.

The only changes are limited to:
 - adding a "#pragma warning( disable:4355 ) // 'this' : used in base
member initializer list" to shut visual C up about the problem (which
should be cleaned up at some point - I found an issue that slipped
through because of that, JDK-8040977)
 - added necessary include file references; I hope the AIX guys can
compile that change to avoid troubles. It compiles fine with all Oracle
supported archs.

There will be another CR for fixing up visibility and cleaning up stuff
a little.

CR:
https://bugs.openjdk.java.net/browse/JDK-8035400

Webrev:
http://cr.openjdk.java.net/~tschatzl/8035400/webrev/

Testing:
perf testing indicated no changes, jprt

Thanks,
  Thomas