(svn r5626) CodeChange : Remove the global _make_screenshot and implement a more flexible mechanism

Simplification of the handling of the main_gui menus,
Removal of repetitions and Hiding the internals of screenshots.
Thanks to glx, Rubidium and Truelight for pointers

screenshot.h

@@ -8,8 +8,15 @@ void InitializeScreenshotFormats(void);
 const char *GetScreenshotFormatDesc(int i);
 void SetScreenshotFormat(int i);
 
+typedef enum ScreenshotType {
+	SC_NONE,
+	SC_VIEWPORT,
+	SC_WORLD
+} ScreenshotType;
+
 bool MakeScreenshot(void);
-bool MakeWorldScreenshot(int left, int top, int width, int height, int zoom);
+void SetScreenshotType(ScreenshotType t);
+bool IsScreenshotRequested(void);
 
 extern char _screenshot_format_name[8];
 extern uint _num_screenshot_formats;