Use setvbuf for world save/load operations

docs/changelog.txt

@@ -19,6 +19,9 @@ USERS
   transparent foregrounds wouldn't draw any char backgrounds.
 + Fixed 3DS renderer crashes that would occur when large numbers
   of sprites were active.
++ File IO for world saving/loading is now buffered, which should
+  improve save/load times on the 3DS and Switch.
++ Enabled writing zip data descriptors for the Switch.
 
 DEVELOPERS
 

src/world.c

@@ -1991,6 +1991,9 @@ static int save_world_zip(struct world *mzx_world, const char *file,
   if(!fp)
     goto err;
 
+  // TODO temporary fix to improve save times on the embedded platforms.
+  setvbuf(fp, NULL, _IOFBF, 16384);
+
   // Header
   if(!savegame)
   {
@@ -2734,6 +2737,9 @@ static FILE *try_open_world(const char *file, boolean savegame,
   if(!fp)
     return NULL;
 
+  // TODO temporary fix to improve load times on the embedded platforms.
+  setvbuf(fp, NULL, _IOFBF, 16384);
+
   if(savegame)
   {
     if(!fread(magic, 5, 1, fp))