[demangler] Fix nested generic lambda

[demangler] Fix nested generic lambda

https://gcc.gnu.org/ml/gcc-patches/2017-09/msg00994.html
	PR demangler/82195
	* cp-demangle.c (d_name): Add 'toplevel' parm.  Pass to	...
	(d_local_name): ... here.  Parse trailing function args on nested
	local_name.
	(d_encoding, d_special_name, d_class_enum_type): Adjust d_name calls.
	* testsuite/demangle-expected: Add tests.

From-SVN: r252815