lib: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

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

Allow lib/msun/logarithm_test to pass on ld128 platforms

For some reason the ld128 log1pl() implementation is less accurate than
logl(), but does at least guarantee precision >= the ld80 implementation.
Mark log1p_accuracy_tests as XFAIL for ld128 and increase the log1p tolerance
to the ld80 equivalent in accuracy_tests to avoid losing test coverage for
the other functions.

PR: 253984
Reviewed By: ngie, dim
Differential Revision: https://reviews.freebsd.org/D29039

Improve test messages for msun tests

Also print the mismatched values when numbers compare not equal.

Reviewed By: dim
Differential Revision: https://reviews.freebsd.org/D29091

Convert the msun tests to ATF

This provides better error messages that just an assertion failure and
also makes it easier to mark individual tests as XFAIL.
It was also helpful when coming up with D28786 and D28787.

Differential Revision: https://reviews.freebsd.org/D28798

logarithm_test: assert that feclearexcept succeeds

This helps ensure that test preconditons are fulfilled.

MFC after: 3 days
Reported by: Coverity
CID: 1346572
Sponsored by: Dell EMC Isilon

Fix warnings in lib/msun/tests/... to help pave way for WARNS?= 6.

- Staticize variables.
- Use nitems liberally. Wherever nitems is used, use unsigned integers
- Remove unused variables (argc, argv, etc)

This fixes most issues -- some issues remain in logarithm_test though.

MFC after: 1 week
Sponsored by: Dell EMC Isilon

Integrate a number of testcases from tools/regression/lib/msun
into the FreeBSD test suite

There's no functional change with these testcases; they're purposely
being left in TAP format for the time being

Other testcases which crash on amd64/i386 as-is have not been
integrated yet (they need to be retested on a later version of
CURRENT, as I haven't used i386 in some time)

MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division