GetBmaskCmt

***********************************************
** get bitmask comment (only for bitfields)
        arguments:      enum_id - id of enum
                        bmask   - bitmask of the constant
                        repeatable - type of comment, 0-regular, 1-repeatable
        returns:        comment attached to bitmask if it exists.
                        otherwise returns 0.

long GetBmaskCmt(long enum_id,long bmask,long repeatable);