Copy provided text to the screen at the provided location. Will not write over an attribute byte
Data String: text to copy to the screen
Data Length: length of STRLEN is active option, otherwise ignored
PS Position: position on the screen to write the text to
Returns
Data Length: may be less than data string length, if an attribute byte is encountered during the copy
RetCode: WHLLTRUNCATED: end of screen reached during copy, WHLLPOSITIONERROR: PSPosition invalid.
