cmfs-tools: add bitmap routines into libcmfs

This patch adds basic bitmap operations into libmcfs as
- libcmfs/bitmap.c
- libcmfs/bitmap.h
All the code are copied from ocfs2-tools/libocfs2/bitmap.{c, h}, and
modified for CMFS.
cmfs-tools: add basic extent_map routines into libcmfs

This commit adds very early and basic extent_map routines into
cmfs-tools/libcmfs/extent_map.c , currently the code is copied from
ocfs2-tools/libocfs2/extent_map.c and modified for CMFS.