Amend Documentation to reflect MS_ERRORFILE requires absolute path.

[ben]

The CONFIG parameter "MS_ERRORFILE" allows the setting of the location to write the mapserver error log.

Currently the documentation at http://mapserver.org/mapfile/map.html gives an example of how to set this.

CONFIG "MS_ERRORFILE" "/var/log/apache/ms_error.log"

but it is not clear that this can only be an absolute reference, and currently cannot be a relative reference (ie from the current mapfile directory, as with other parameters) (see ticket:2853)

cheers

Ben

[jmckenna]

- updated the MAP document for the ms_errorfile absolute path requirement - committed in svn