RFR (M): 8184346: Clean up G1CMBitmap

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that tries to clean up (and only
clean up) the G1CMBitMap class (and the surrounding helper classes) a
bit?

What has been done:
- fix naming
- improve visibility of methods
- remove superfluous code
- make G1CMBitMapClosure pass a HeapWord* instead of a bitmap index,
avoiding that the user code is cluttered with conversions from bitmap
indices to HeapWords
- remove inheritance between G1CMBitMap and G1CMBitMapRO, similar to
the BitMap class make G1CMBitMapRO a "view" of G1CMBitMap.
- remove unused code in G1CMBitMapRO
- move method implementations into .inline.hpp file

The next CR JDK-8184347 will deal with moving G1CMBitmap* into separate
files.

CR:
https://bugs.openjdk.java.net/browse/JDK-8184346
Webrev:
http://cr.openjdk.java.net/~tschatzl/8184346/webrev/
Testing:
jprt

Thanks,
  Thomas