Fix first run crashing on Xbox One. Added savestate support. Rewind … (#87)

* Fix first run crashing on Xbox One.
* Added savestate support.
* Rewind works.  Fixes issue #83 and possibly #49.
* Added Disc Control menu.  Supports Disks, Tapes and M3U files (issue #66).
* Added in support for 5200 Super Carts.
* Better support for 5200 controller.
* Added Paddle support.
* Converted Core Options menu to v2.
* Moved some core options into submenus.
* Added controller mappings for Ports 2-4.
* Added options for Dual Stick and Swap Ports.  Fixes issue #76.
* Joystick/Console now controlled more easily with device type Atari Keyboard.
* Added 4 Hi-Res Artifacting modes.  Restart does something now.
* When core option changed only reboot if necessary.  Removed several hardcoded controller binds.  Fixed issue #29.  Joypad input ignored when virtual keyboard active.
* SIO Acceleration now defaults to enabled.  Fix for Bounty Bob (5200 & lift fix A800).
* Added Atari 800 carts to autodetect DB.
* Added more Carts to DB.
* Fixed Drive Index not being reset on 'restart'.
* Changed Atari Joystick default mappings to something more reasonable.

libretro/retro_strings.h

@@ -0,0 +1,32 @@
+/* Copyright (C) 2018 
+ *
+ * Permission is hereby granted, free of charge,
+ * to any person obtaining a copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef RETRO_STRINGS_H__
+#define RETRO_STRINGS_H__
+
+#include <stdbool.h>
+
+//*****************************************************************************
+// String helpers functions
+char* trimwhitespace(char *str);
+char* strleft(const char* str, int len);
+char* strright(const char* str, int len);
+bool strstartswith(const char* str, const char* start);
+bool strendswith(const char* str, const char* end);
+
+#endif