Add hook to insert_with_markers() so theme/plugin authors can prevent writing to .htaccess

[alimony]

If not using .htaccess to rewrite, but instead keeping those settings in an Apache config file, it would be nice if writing the .htaccess file could be prevented by hooking into the function that does that (e.g. returning false or something like that).

Why? If the Apache option AllowOverride is turned off (which it should be for performance reasons, if not using any .htaccess files) the file won't ever be read. But still having it around (except cluttering) can possibly confuse someone having access to the server, seeing the file and thinking it actually controls anything. Especially since most WordPress support threads on the Internet assumes that an .htaccess file is used for rewrite rules.

One solution is to keep an empty, non-writable .htaccess file, optionally having a comment in it saying it's unused, but getting rid of the file altogether would be much cleaner. Also, it can still happen that someone accidentally changes the file permission, and someone else (or the same person) saves permalink options, saving a new .htaccess file, having created the possibility of confusion once again.