Make the windows-nat.c target inherit inf-child.c.

Make the windows-nat.c target inherit inf-child.c.

So that all native targets inherit a single "superclass".

Target methods that are set to or do the same as inf-child.c's are
removed.

Tested by cross building on Fedora 17, and then confirming that

./gdb.exe ./gdb.exe -ex "set pagination off" -ex "start"

under Wine still works.

Also, Joel tested this with Adacore's internal testsuite.

gdb/
2014-03-12  Pedro Alves  <palves@redhat.com>

	* windows-nat.c: Include inf-child.h.
	(windows_ops): Delete global.
	(windows_open, windows_prepare_to_store, windows_can_run): Delete
	methods.
	(init_windows_ops): Delete function.
	(windows_target): New function, based on init_windows_ops, but
	inherit inf_child_target.
	(_initialize_windows_nat): Use windows_target.  Install x86
	specific target methods here.