lib/msun: Cleanup after $FreeBSD$ removal

Remove no longer needed explicit inclusion of sys/cdefs.h.

PR: 276669
MFC after: 1 week

lib: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

libm: remove unused variables for LDBL_MANT_DIG != 113

Sponsored by: The FreeBSD Foundation

* msun/man/cosh.3:
* msun/man/sinh.3:
* msun/man/tanh.3:
. Fix grammar.

* msun/src/e_coshl.c:
* msun/src/e_sinhl.c:
. Fix comment.

* msun/src/s_tanhl.c:
. Remove unused variables.
. Fix location/indentation of comments.
. Use comparison involving ints instead of long double.
. Re-order polynomial evaluation on ld128 for |x| < 0.25.
For now, retain the older order in an "#if 0 ... #else" block.
. Use int comparison to short-circuit the |x| < 1.5 condition.

Requested by: bde

* Makefile:
. Hook coshl, sinhl, and tanhl into libm.
. Create symbolic links for corresponding manpages.
. While here remove a nearby extraneous space.

* Symbol.map:
* src/math.h:
. Move coshl, sinhl, and tanhl to their proper locations.

* man/cosh.3:
* man/sinh.3:
* man/tanh.3:
. Update the manpages.

* src/e_cosh.c:
* src/e_sinh.c:
* src/s_tanh.c:
. Add weak reference for LBDL_MANT_DIG==53 targets.

* src/imprecise.c:
. Remove the coshl, sinhl, and tanhl kludge.

* src/e_coshl.c:
. ld80 and ld128 implementation of coshl().

* src/e_sinhl.c:
. ld80 and ld128 implementation of sinhl().

* src/s_tanhl.c:
. ld80 and ld128 implementation of tanhl().

Obtained from: bde (mostly), das and kargl