RFR (S): 8184347: Move G1CMBitMap and support classes into their own files

[Thomas Schatzl]

Hi all,

  can I have reviews for this wrap-up of the G1CMBitmap cleanup? It
simply moves all G1CMBitmap related code into their own files.

Although it's a large change, it's really only moving code.

Depends on JDK-8184346, based on webrev.3.

CR:
https://bugs.openjdk.java.net/browse/JDK-8184347
Webrev:
http://cr.openjdk.java.net/~tschatzl/8184347/webrev/
Testing:
jprt

Thomas