Split BitVector into its own file.

This just pulls the BitVector stuff out into separate files.

IIRC the motivation for building Misc.c for ARM rather than Thumb was
the bit-manipulation going on in BitVector (e.g. the use of ffs()),
so I switched that around in the makefile.

The only change of any substance was relocation of the kBitVectorGrowth
define from the .h to the .c.

Change-Id: Ib35fda81809081bd629b4f344e41f21966e1441c
6 files changed