Windows: Always set the system timer resolution to 1ms by default.

An existing hint lets apps that don't need the timer resolution changed avoid
this, to save battery, etc, but this fixes several problems in timing, audio
callbacks not firing fast enough, etc.

Fixes Bugzilla #2944.

visualtest/include/SDL_visualtest_screenshot.h

@@ -0,0 +1,50 @@
+/* See COPYING.txt for the full license governing this code. */
+/**
+ * \file SDL_visualtest_screenshot.h
+ *
+ * Header for the screenshot API.
+ */
+
+#include "SDL_visualtest_process.h"
+
+#ifndef _SDL_visualtest_screenshot_h
+#define _SDL_visualtest_screenshot_h
+
+/* Set up for C function definitions, even when using C++ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Takes a screenshot of each window owned by the process \c pinfo and saves 
+ * it in a file \c prefix-i.png where \c prefix is the full path to the file 
+ * along with a prefix given to each screenshot.
+ *
+ * \return 1 on success, 0 on failure.
+ */
+int SDLVisualTest_ScreenshotProcess(SDL_ProcessInfo* pinfo, char* prefix);
+
+/**
+ * Takes a screenshot of the desktop and saves it into the file with path
+ * \c filename.
+ *
+ * \return 1 on success, 0 on failure.
+ */
+int SDLVisualTest_ScreenshotDesktop(char* filename);
+
+/**
+ * Compare a screenshot taken previously with SUT arguments \c args that is
+ * located in \c test_dir with a verification image that is located in 
+ * \c verify_dir.
+ *
+ * \return -1 on failure, 0 if the images were not equal, 1 if the images are equal
+ *         and 2 if the verification image is not present.
+ */
+int SDLVisualTest_VerifyScreenshots(char* args, char* test_dir, char* verify_dir);
+
+/* Ends C function definitions when using C++ */
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SDL_visualtest_screenshot_h */