Added clock: u8 field to Cond struct that stores the clock
setting (CLOCK_REALTIME or CLOCK_MONOTONIC) per pthread_condattr.
pthread_cond_init now properly sets the clock attribute.
timedwait uses the stored clock instead of hardcoding CLOCK_REALTIME.
Previously pthread_cond_init with CLOCK_MONOTONIC would log TODO
and use the wrong clock, causing condition variable timeouts to
behave incorrectly.
pthread_cond_t size updated from 8 to 12 bytes to accommodate
the new field. Cross-referenced with POSIX pthread_cond_init(3)
and Linux glibc nptl pthread_cond_init.c.