PR c++/48969
	PR c++/44175
gcc/c-family/
	* c-common.c (max_tinst_depth): Lower default to 900.
gcc/cp/
	* error.c (subst_to_string): New.
	(cp_printer): Use it for 'S'.
	(print_instantiation_partial_context_line): Handle subst context.
	* pt.c (push_tinst_level): Handle subst context.
	(deduction_tsubst_fntype): Don't track specific substitutions.
	Use push_tinst_level.

From-SVN: r174772