* mem-break.c (struct raw_breakpoint): New field shlib_disabled.

	* mem-break.c (struct raw_breakpoint): New field shlib_disabled.
	(set_gdb_breakpoint_at): If GDB is inserting a breakpoint on top
	of another, then delete the previous, and validate all
	breakpoints.
	(validate_inserted_breakpoint): New.
	(delete_disabled_breakpoints): New.
	(validate_breakpoints): New.
	(check_mem_read): Validate breakpoints before trusting their
	shadow.  Delete disabled breakpoints.
	(check_mem_write): Validate breakpoints before trusting they
	should be inserted.  Delete disabled breakpoints.
	* mem-break.h (validate_breakpoints):
	* server.c (handle_query): Validate breakpoints when we see a
	qSymbol query.