* manual/threads.texi (pthread_key_create, pthread_key_delete,
pthread_getspecific, pthread_setspecific): Format with
@deftypefun, and add @safety note.
* manual/signal.texi: Move comments that analyze the above
functions to their home place.
* manual/users.texi: Document MTASC-safety properties.
* manual/macros.texi: Add comments before MTASC-safety macros.
Fix manual build warnings.

The mixed use of automatic and manual node next, previous,
and top specification causes warning when building the manual.
This fix explicitly specifies the node's next, previous and top
values to fix the warning.
[hppa] Regenerate libm-test-ulps.

Regenerate libm-test-ulps from scratch.
Remove excessive redundant ChangeLog header lines.
Update x86_64 ULPs (AMD Family 10h)
Update x86_64 ULPs (AMD family 21, model 2)

Tested on an AMD FX-8320 CPU