c++: Fix -Wvexing-parse ICE with omitted int [PR97762]
For declarations like
long f();
decl_specifiers->type will be NULL, but I neglected to handle this case,
therefore we ICE. So handle this case by pretending we've seen 'int',
which is good enough for -Wvexing-parse's purposes.
gcc/cp/ChangeLog:
PR c++/97762
* parser.c (warn_about_ambiguous_parse): Handle the case when
there is no type in the decl-specifiers.
gcc/testsuite/ChangeLog:
PR c++/97762
* g++.dg/warn/Wvexing-parse8.C: New test.