Enable error trapping and reset error and warning count
Description
The routine gSetErrorTrap() enables or disables error trapping, according to the value of sw. The default is for error trapping to be switched off. When error trapping is enabled, any errors or warnings that are generated are counted. The count is returned by gEnqNumberOfErrors() and it is reset whenever gSetErrorTrap(GON) is called. The count maintained for the purposes of error trapping is quite separate from the main error and warning count that is returned by gEnqLastErrors().