docs: heavy editing to make this happy with latest wikibridge.

The public headers saw lots of cleanups, backporting from SDL3 docs, and
merging with the wiki.

The markdown files in docs/README-*.md were converted to Unix endlines.

include/SDL_mutex.h

@@ -112,13 +112,13 @@ extern "C" {
 #endif
 
 /**
- *  Synchronization functions which can time out return this value
- *  if they time out.
+ * Synchronization functions which can time out return this value if they time
+ * out.
  */
 #define SDL_MUTEX_TIMEDOUT  1
 
 /**
- *  This is the timeout value which corresponds to never time out.
+ * This is the timeout value which corresponds to never time out.
  */
 #define SDL_MUTEX_MAXWAIT   (~(Uint32)0)