Increase q3_ui .arena filename list buffer size to 4096 bytes

Allow listing about 273 .arena filenames for loading in q3_ui instead
of only about 136 that fit in a 2048 byte buffer (average 15 bytes per
file name).

The buffer for filename list runs out of space long before the buffer
for arena file content does. There is no warning for file list out of
space but there is a warning for arena file content.

This was requested by a user with many maps.

code/q3_ui/ui_gameinfo.c

@@ -169,7 +169,7 @@ static void UI_LoadArenas( void ) {
 	int			numdirs;
 	vmCvar_t	arenasFile;
 	char		filename[128];
-	char		dirlist[2048];
+	char		dirlist[4096];
 	char*		dirptr;
 	int			i, n;
 	int			dirlen;
@@ -188,7 +188,7 @@ static void UI_LoadArenas( void ) {
 	}
 
 	// get all arenas from .arena files
-	numdirs = trap_FS_GetFileList("scripts", ".arena", dirlist, 2048 );
+	numdirs = trap_FS_GetFileList("scripts", ".arena", dirlist, 4096 );
 	dirptr  = dirlist;
 	for (i = 0; i < numdirs; i++, dirptr += dirlen+1) {
 		dirlen = strlen(dirptr);