minimal fixes to visual test, so that it actually builds w/o warnings:

- linux_process.c: add an SDLVisualTest_ScreenshotProcess() stub for
  linux builds succeed.
- action_configparser.c: fixes -Wswitch warnings.
- testharness.c: fixes 'is used uninitialized' warnings for userevents.
- testharness.c: fixes format string argument to 'Force killing...'
- testquit.c: fix type of options array in main().
- windows_screenshot.c: lowercase windows.h header name.
- ran dos2unix on all sources and add missing newlines at files' ends.
- minor adjustments to autotools build system (which actually seems to
  need more surgery for unnecessary stuff...)

visualtest/src/action_configparser.c

@@ -36,6 +36,9 @@ FreeAction(SDLVisualTest_Action* action)
             action->extra.process.args = NULL;
         }
         break;
+
+      default:
+        break;
     }
 }