gdb/testsuite/

	gdb/testsuite/
	* gdb.trace/unavailable.cc (struct Virtual): New.
	(virtualp): New global pointer.
	* gdb.trace/unavailable.exp (gdb_collect_globals_test): Test
	printing a pointer to an object whose type has a vtable, with
	print object on.

	gdb/
	* value.h (value_entirely_available): Declare.
	* value.c (value_entirely_available): New function.
	* c-valprint.c (c_value_print): Don't try fetching the pointer's
	real type if the pointer is unavailable.