Update chgdbmailusers.c

I edited this file because password plugin, does not run on my system using dbmail driver.

The reason are:
- on first, on many places the function password_save, is referenced as save, and I had to change the name of this function on drivers/dbmail.php:
- At the file helpers/chgdbmailusers.c, once solved the first problem, when I intended to change a pass, it changes but the page returns an error.  This error dissapears using #define RCOK 0

Sorry for my english ;)