To protect FIPS-related global variables, add locking mechanisms

To protect FIPS-related global variables, add locking mechanisms
around them.

NOTE: because two new locks are added, this adds potential binary
incompatibility with earlier versions in the 0.9.7 series.  However,
those locks will only ever be touched when FIPS_mode_set() is called
and after, thanks to a variable that's only changed from 0 to 1 once
(when FIPS_mode_set() is called).  So basically, as long as FIPS mode
hasn't been engaged explicitely by the calling application, the new
locks are treated as if they didn't exist at all, thus not becoming a
problem.  Applications that are built or rebuilt to use FIPS
functionality will need to be recompiled in any case, thus not being a
problem either.