* class.c (get_enclosing_class): New function.
	(is_base_of_enclosing_class): Likewise.
	* cp-tree.h (get_enclosing_class): Declare.
	(is_base_of_enclosing_class): Likewise.
	* pt.c (coerce_template_parms): Use them.
	* g++spec.c (lang_specific_driver): Check whether MATH_LIBRARY is
	null to decide whether to use it.

From-SVN: r22343