Endian fixes:

The library output is host-endian, however the player side assumes
little endian basically cause the original author got lazy on the
player :)  [ See: http://sf.net/p/wildmidi/support-requests/2/ . ]
Fix this by using SND_PCM_FORMAT_S16 instead of SND_PCM_FORMAT_S16_LE
in alsa, and AFMT_S16_NE instead of AFMT_S16_LE in oss output code.
add endian check to cmake.