Handle corner case for abstract decls

sometimes abstract decls in parameter lists left the returned name
uninitialized potentially leading to segfaults, like in

  int f(int ()) {
    return 0;
  }

Deal with this.

tccgen.c

@@ -4591,12 +4591,14 @@ static CType *type_decl(CType *type, AttributeDef *ad, int *v, int td)
 	    parse_attribute(ad);
 	    post = type_decl(type, ad, v, td);
 	    skip(')');
-	}
+	} else
+	  goto abstract;
     } else if (tok >= TOK_IDENT && (td & TYPE_DIRECT)) {
 	/* type identifier */
 	*v = tok;
 	next();
     } else {
+  abstract:
 	if (!(td & TYPE_ABSTRACT))
 	  expect("identifier");
 	*v = 0;

tests/tests2/60_errors_and_warnings.c

@@ -130,4 +130,15 @@ static enum myenum { L = -1 } L;
 void foo(void) {
 static enum myenum { L = -1 } L;                                                
 }
+#elif defined test_abstract_decls
+int bar(const char *());     // abstract declarator here is okay
+int bar (const char *(*g)()) // should match this 'g' argument
+{
+  g();
+  return 42;
+}
+int foo(int ())              // abstract decl is wrong in definitions
+{
+  return 0;
+}
 #endif

tests/tests2/60_errors_and_warnings.expect

@@ -59,3 +59,6 @@
 
 [test_duplicate_def_2]
 60_errors_and_warnings.c:131: error: redeclaration of 'L'
+
+[test_abstract_decls]
+60_errors_and_warnings.c:141: error: identifier expected