SDL: README-migration.md: Updated stdio RWops example code for new API.

From 3b5780ba0a5d9d755ef47f5c40936a88bf15a0cb Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 15 Dec 2022 11:20:29 -0500
Subject: [PATCH] README-migration.md: Updated stdio RWops example code for new
 API.

---
 docs/README-migration.md | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/docs/README-migration.md b/docs/README-migration.md
index 1891fee97d48..dea54ff72803 100644
--- a/docs/README-migration.md
+++ b/docs/README-migration.md
@@ -152,28 +152,28 @@ stdio_seek(SDL_RWops * context, Sint64 offset, int whence)
     return SDL_Error(SDL_EFSEEK);
 }
 
-static size_t SDLCALL
-stdio_read(SDL_RWops * context, void *ptr, size_t size, size_t maxnum)
+static Sint64 SDLCALL
+stdio_read(SDL_RWops * context, void *ptr, Sint64 size)
 {
     size_t nread;
 
-    nread = fread(ptr, size, maxnum, (FILE *)context->hidden.stdio.fp);
+    nread = fread(ptr, 1, (size_t) size, (FILE *)context->hidden.stdio.fp);
     if (nread == 0 && ferror((FILE *)context->hidden.stdio.fp)) {
-        SDL_Error(SDL_EFREAD);
+        return SDL_Error(SDL_EFREAD);
     }
-    return nread;
+    return (Sint64) nread;
 }
 
-static size_t SDLCALL
-stdio_write(SDL_RWops * context, const void *ptr, size_t size, size_t num)
+static Sint64 SDLCALL
+stdio_write(SDL_RWops * context, const void *ptr, Sint64 size)
 {
     size_t nwrote;
 
-    nwrote = fwrite(ptr, size, num, (FILE *)context->hidden.stdio.fp);
+    nwrote = fwrite(ptr, 1, (size_t) size, (FILE *)context->hidden.stdio.fp);
     if (nwrote == 0 && ferror((FILE *)context->hidden.stdio.fp)) {
-        SDL_Error(SDL_EFWRITE);
+        return SDL_Error(SDL_EFWRITE);
     }
-    return nwrote;
+    return (Sint64) nwrote;
 }
 
 static int SDLCALL