Update the Settings.php file.
The most important function in this file for mod makers happens to be the
updateSettingsFile() function, but it shouldn't be used often anyway.
- updates the Settings.php file with the changes supplied in config_vars.
- expects config_vars to be an associative array, with the keys as the
variable names in Settings.php, and the values the variable values.
- does not escape or quote values.
- preserves case, formatting, and additional options in file.
- writes nothing if the resulting file would be less than 10 lines
in length (sanity check for read lock.)
- check for changes to db_last_error and passes those off to a separate handler
- attempts to create a backup file and will use it should the writing of the
new settings file fail