Remove regcache_xfree

Remove regcache_xfree

This removes regcache_xfree in favor of plain "delete".

gdb/ChangeLog
2017-09-25  Tom Tromey  <tom@tromey.com>

	* spu-tdep.c (spu2ppu_dealloc_cache): Use delete.
	* regcache.h (regcache_xfree): Don't declare.
	* regcache.c (regcache_xfree): Remove.
	(do_regcache_xfree): Use delete.
	* ppc-linux-tdep.c (ppu2spu_dealloc_cache): Use delete.
	* linux-fork.c (free_fork): Use delete.
	(fork_save_infrun_state): Likewise.
	* jit.c (jit_dealloc_cache): Use delete.
	* infrun.c (discard_infcall_suspend_state): Use delete.