src/libpcp/lock.c: fix Mac OS X compilation failure
src/libpcp/lock.c: fix Mac OS X compilation failure

Recent locking changes broke the code in the HAVE___THREAD undefined
block of __pmInitLocks().

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp