(followup to r4145) Non-functional change:

Change the os_atomic_increment() and os_compare_and_swap() functions
to macros to avoid artificial limitations on the types of those
functions' arguments. As a consequence typecasts from the source
code can be removed.

Also remove Google's copyright from os0sync.ic because that file no longer
contains code from Google.

Approved by:	Marko (rb://88), also ok from Inaam via IM