Re: Add minimal C example and SQL registration example for custom table access methods.

Suggestion:

In the C example you added you mention in the comment:

+  /* Methods from TableAmRoutine omitted from example, but all
+     non-optional ones must be provided here. */

Perhaps you could provide a "see <xyz>" to point the reader finding your example where he could find these non-optional
methodshe must provide?
 

Nitpicking a little: your patch appears to change more lines than it does, because it added line breaks earlier in the
lines.I would generally avoid that unless there's good reason to do so.