RFR: 8287661: Fix and improve BitMap::print_on(outputStream*)

[Aleksey Shipilev]

Found these inconvenient during debugging using the `BitMap::print_on`. We pass the `outputStream*` to the method, but do not use it. Also, the output is hard to read for large bitmaps. 

Sample output generated by gtest:


Bitmap (0 bits):
Bitmap (128 bits):
    0: .......... .......... .......... .......... ..........
   50: .......... ....S..... .......... .......... ..........
  100: .......... .......... ........
Bitmap (1024 bits):
    0: .......... .......... .......... .......... ..........
   50: .......... .......... .......... .......... ..........
  100: .......... .......... .......... .......... ..........
  150: .......... .......... .......... .......... ..........
  200: .......... .......... .......... .......... ..........
  250: .......... .......... .......... .......... ..........
  300: .......... .......... .......... .......... ..........
  350: .......... .......... .......... .......... ..........
  400: .......... .......... .......... .......... ..........
  450: .......... .......... .......... .......... ..........
  500: .......... ..S....... .......... .......... ..........
  550: .......... .......... .......... .......... ..........
  600: .......... .......... .......... .......... ..........
  650: .......... .......... .......... .......... ..........
  700: .......... .......... .......... .......... ..........
  750: .......... .......... .......... .......... ..........
  800: .......... .......... .......... .......... ..........
  850: .......... .......... .......... .......... ..........
  900: .......... .......... .......... .......... ..........
  950: .......... .......... .......... .......... ..........
 1000: .......... .......... ....


It becomes clearer that bits 64 and 512 are set, respectively.

Additional testing:
 - [x] Linux x86_64 fastdebug, new gtest
 - [x] Linux x86_64 release, new gtest

-------------

Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/8970/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8970&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287661
  Stats: 33 lines in 2 files changed: 30 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8970.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8970/head:pull/8970

PR: https://git.openjdk.java.net/jdk/pull/8970