[CPP-340] Fix TooFewArguments.c to actually provide a ()-prototype.

cpp/ql/src/Likely Bugs/UnderspecifiedFunctions/TooFewArguments.c

@@ -1,8 +1,9 @@
-
-void one_argument(int x);
+void one_argument();
 
 void calls() {
 	one_argument(1); // GOOD: `one_argument` will accept and use the argument
 	
 	one_argument(); // BAD: `one_argument` will receive an undefined value
 }
+
+void one_argument(int x);