libpcp: fix minor tz.c typos and clarify some comments
libpcp: fix minor tz.c typos and clarify some comments

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