gdb/doc: move @menu blocks to the end of their enclosing @node

gdb/doc: move @menu blocks to the end of their enclosing @node

The @menus should be at the end of a @node.  We mostly get this right,
but there's a few places where we don't.  This commit fixes the 5
places we get this wrong.

I manually checked the info page and read each of the offending nodes
after this change and I believe they all still make sense with the
menu moved.

gdb/doc/ChangeLog:

	* gdb.texinfo (Specify Location): Move menu to the end of the
	node.
	(Auto-loading): Likewise.
	(Extending GDB): Likewise.
	(TUI): Likewise.
	(Operating System Information): Likewise.