Added _EXPORT_INT macro to export an integer constant to Python-space.
Use it for all the AFMT_* constants, and update the list of AFMT_*
constants to match what's in Linux 2.4: add AFMT_{QUERY,IMA_ADPCM,
MPEG,AC3}.  This should probably be tested with older versions of OSS,
eg. with Linux 2.2 and 2.0.

Export all SNDCTL_* ioctl numbers (where "all" is the set found in
/usr/include/linux/soundcard.h on my Debian 3.0 system -- again
Linux 2.4).  Again needs to be tested with older OSS versions.