MFC r320755,r320762,r320893:
BIT_FLS(9).

MFC r318781:
Add BIT_OR2(), BIT_AND2(), BIT_NAND2(), BIT_XOR() and BIT_XOR2().

Approved by: re (marius)

MFC r303519

Fix two return types in the cpuset(9) and bitset(9) man pages

The *_FFS() and *_COUNT() functions return int, not size_t.

Approved by: re (gjb)
Sponsored by: Dell Inc.