Add semicolons to xm_popcount and uncomment fls

`xm_popcount` had some missing semicolons at the end of the lines,
not sure if this was intended but gcc 4.6 did not like it.  Adding
in the semicolons allowed compilation of the source.
the `fls` function defined in `msutil.h` was commented out which was
causing `msutil_t.c` to fail. Uncommenting the function solved the
problem