pt.c (tsubst_aggr_type): Bail if creating the argvec fails.

        * pt.c (tsubst_aggr_type): Bail if creating the argvec fails.
        (tsubst_template_arg_vector): Likewise.

From-SVN: r35592

gcc/testsuite/g++.old-deja/g++.pt/explarg1.C

+// Bug: g++ generates an error trying to generate the first foo<int>, when
+// it should silently fail and go on to the next one.
+
+template<class T, typename U> class A { };
+
+template<class T> void
+foo(const A<T,typename T::N>&);
+
+template<typename T>
+class B { };
+
+template<typename T> void
+foo(B<T> const &) { }
+
+int
+main(void)
+{
+  B<int> sa;
+
+  foo<int> (sa);
+}