Mark internal time functions with attribute_hidden [BZ #18822]
Mark internal time functions with attribute_hidden to allow direct
access within libc.so and libc.a without using GOT nor PLT.
[BZ #18822]
* include/time.h (__tzstring): Add attribute_hidden.
(__tzfile_read): Likewise.
(__tzfile_compute): Likewise.
(__tzfile_default): Likewise.
(__tzset_parse_tz): Likewise.
(__offtime): Likewise.
(__asctime_r): Likewise.
(__tzset): Likewise.
(__tz_convert): Likewise.
(__getdate_r): Likewise.
(__getclktck): Likewise.