mpsetups: a bunch of bug fixes

- "load settings" becoming invalid when entering and exiting the challenges screen
- when setting a setup as default, it would change the current setup
- larger window width causing the marquee text to be rendered off-bounds
- reduced the setup name's max length, as it wouldn't fit on the screen in some cases

src/include/constants.h

@@ -4757,7 +4757,7 @@ enum weaponnum {
 #define EXTRA_SLEEP_TIME 1000LL // 100us
 
 #define MPSETUP_MAXSETUPS 128
-#define MPSETUP_MAXNAME 18
+#define MPSETUP_MAXNAME 17
 #define MPSETUP_BLOCKSIZE 80
 
 #endif

src/include/types.h

@@ -3983,13 +3983,14 @@ struct menu {
 	union {
 		struct menudata_endscreen endscreen;
 		struct menudata_main main;
-		struct menudata_mpsetup mpsetup;
 		struct menudata_mppause mppause;
 		struct menudata_mpend mpend;
 		struct menudata_filemgr fm;
 		struct menudata_main4mb main4mb;
 		struct menudata_training training;
 	};
+
+	struct menudata_mpsetup mpsetup;
 };
 
 struct gamefile {