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/

Remove amd64 XFAIL from tests/lib/msun/fma_test:infinities

This test no longer fails after 3b00222f156dca5700c839d73e36daf479fa640c.

PR: 205448
MFC after: 1 week

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

fma_test: mute a warning about unreachable code on amd64 by restructuring
the #ifdef block to only handle the rest of the logic in the loop in the
#else case.

MFC after: 3 days
Reported by: Coverity
CID: 1346844
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

Use j instead of a hardcoded index (9) and increment it after
running the NaNs testcases

MFC after: 3 days
Pointyhat to: ngie
Sponsored by: EMC / Isilon Storage Division

Integrate the remaining tools/regression/lib/msun testcases into the
FreeBSD test suite under lib/msun/tests

MFC after: 3 weeks
X-MFC with: r292328
Sponsored by: EMC / Isilon Storage Division