Fixed SetTextAlign(), SetBkMode(), SetROP2(), SetPolyFillMode(), and

Fixed SetTextAlign(), SetBkMode(), SetROP2(), SetPolyFillMode(), and
SetStretchBltMode() to assume that the corresponding DC driver
functions return only a BOOL success flag, and therefore a proper
return value should be generated by the main function. Fixed
EMFDRV_StretchDIBits() to return a proper value (like
MFDRV_StretchDIBits already does). Added comments about other cases of
improper return values.