Use SIGTRAP si_code values for all FreeBSD architectures on 11.3 and later.

Use SIGTRAP si_code values for all FreeBSD architectures on 11.3 and later.

Fixes to set correct si_code values (such as TRAP_BRKPT) were made to
the remaining FreeBSD architectures (MIPS and sparc64) in the head
branch leading up to 12.0 and were merged back between the 11.2 and
11.3 releases.

gdb/ChangeLog:

	* fbsd-nat.h: Include <osreldate.h>.  Define USE_SIGTRAP_SIGINFO
	for all architectures on FreeBSD 11.3 and later.