opr: implement the BSD ffs() functions

opr: implement the BSD ffs() functions

Provide opr implementations of ffs(), fls(), ffsll(), and flsll().
There is no need to provide the 'long' form, since int is 32 bits
and long long is 64 bits.

These functions return the index of the first (or last) bit set
in a given (long long) word, or zero if no bits are set.

Change-Id: I126000f8b650f41d67567a9af659e0805478af2d
Reviewed-on: http://gerrit.openafs.org/11671
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Daria Brashear <shadow@your-file-system.com>