Fix undefined behaviour in C code problem

Without the return, this code would core dump, depending
on compiler version. The compiler was generating a warning
too about the missing return.

Part of eclipse-cdt#816

dsf-gdb/org.eclipse.cdt.tests.dsf.gdb/data/launch/src/StepIntoSelectionTestApp.cc

@@ -63,6 +63,7 @@ int laterLineNotHitTest() {
 int laterLineDifferentFileTest() {
     int b = 0;
     value();  // LATER_LINE_DIFFERENT_FILE_LINE
+    return 0;
 }
 
 int differentFileTest() {