Fix detection of "r_fs" and "r_gs" on FreeBSD.

Fix detection of "r_fs" and "r_gs" on FreeBSD.

Include <sys/types.h> as a prerequisite for <machine/reg.h> when checking
for the r_fs and r_gs members in struct reg.  Note that the previous test
for <machine/reg.h> already includes <sys/types.h> as a prerequisite.

gdb/ChangeLog:

	* configure.ac: Include <sys/types.h when checking for "r_fs" in
	"struct reg".
	* configure: Regenerate.