c++: unexpanded pack in var tmpl partial spec [PR100652]

c++: unexpanded pack in var tmpl partial spec [PR100652]

Here we're failing to spot a bare parameter pack appearing in the argument
list of a variable template partial specialization because we only look for
them within the decl's TREE_TYPE, which is sufficient for class templates
but not for variable templates.

	PR c++/100652

gcc/cp/ChangeLog:

	* pt.c (push_template_decl): Check for bare parameter packs in
	the argument list of a variable template partial specialization.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/var-templ69.C: New test.