src/libpcp/src/lock.c: fix initialization error in roll-your-own TPD
src/libpcp/src/lock.c: fix initialization error in roll-your-own TPD

If the compiler does not support thread-private-data, then we do
our own implementation.  This is not used on most platforms.
But the code contained a lurking intialization error and on Mac OS X
it blew up.  Fix is simple, and memset() is your friend.

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