minor tidy-up in GetOutput()
refuse loading suspiciouly long files (backport WM_ERR_LONGFIL from 0.4.x)
Fix the roundtempo option which had been broken since its invention
in 0.2.3.5 (WM_MO_ROUNDTEMPO: was 0xA000 instead of 0x2000.) Fix the
invalid option checking in WildMidi_Init().