Use host_address_to_string in compile_cplus_instance::enter_scope

Use host_address_to_string in compile_cplus_instance::enter_scope

This patch fixes a problem being reported by the buildbot with an
invalid argument to a "%p" printf format. Instead of "%p", the
debug output is changed to use "%s" and host_address_to_string.

gdb/ChangeLog

	* compile/compile-cplus-types.c (compile_cplus_instance::enter_scope):
	Use "%s" and host_address_to_string instead of "%p" in printf.