* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S: Use
DW_CFA_advance_loc2 for .Laddl-.Lsubl.
* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S: Use
DW_CFA_advance_loc for .Laddl-.Lsubl.
* sysdeps/unix/sysv/linux/i386/sysdep-cancel.h: Don't use
position-independent unwind data for static libraries.
Add missing unwind info. Add comments.