gdb: move ptrace.m4 to gdbsupport

gdb: move ptrace.m4 to gdbsupport

ptrace.m4, providing the GDB_AC_PTRACE autoconf macro, is used by gdb,
gdbserver and gdbsupport.  I think it would make sense to move it to
gdbsupport.

gdb/ChangeLog:

	* acinclude.m4: Update ptrace.m4 path.
	* ptrace.m4: Moved to gdbsupport.

gdbserver/ChangeLog:

	* acinclude.m4: Update ptrace.m4 path.

gdbsupport/ChangeLog:

	* Makefile.in: Re-generate.
	* acinclude.m4: Update ptrace.m4 path.
	* ptrace.m4: Move here.

Change-Id: I849c149fd5dd8c3b2b0af38654fb353e3727871b