go32-nat.c: Don't install a deprecated_xfer_memory method

go32-nat.c: Don't install a deprecated_xfer_memory method

This removes yet another instance of a deprecated_xfer_memory user.

Unfortunately djgpp's write_child function takes a non-const buffer
pointer, while GDB's xfer_partial api passes a const pointer.  To be
const-correct, we need to copy that buffer to a non-const buffer, and
pass the copy to write_child.  This is actually what
target.c:default_xfer_partial itself does, when calling into the
ops->deprecated_xfer_memory hook.

Tested by cross-building djgpp gdb, on x86-64 Fedora 17.

gdb/
2014-02-26  Pedro Alves  <palves@redhat.com>

	* go32-nat.c (my_write_child): New function.
	(go32_xfer_memory): Rewrite as to_xfer_partial helper.
	(go32_xfer_partial): New function.
	(init_go32_ops): Don't install a deprecated_xfer_memory hook.
	Instead install a to_xfer_partial hook.