Don't require MIDI sysex data to have the high bit clear
Store and use an ALbuffer for samples in an ALfontsound

The fontsound still maintains its own start, end, and loop offsets, so that the
same buffer may be shared between multiple/all fontsounds. Ideally a single
buffer should be used for all fontsounds to avoid memory fragmentation and help
CPU caching, although higher quality soundfonts may need more memory than a
single buffer can hold.
Load soundfont samples into an ALbuffer

Also remove ALsoundfont's now-unneeded sample storage functions and struct
fields.