PaUtil_AllocateMemory doc omits value for alignment guarantees

[rossb]

The current documentation for PaUtil?_AllocateMemory reads:

Allocate size bytes, guaranteed to be aligned to a FIXME byte boundary <<

We should decide whether we want to make alignment guarantees. Recent discussions re the ringbufer imply that we should at least make some minimal guarantee (such as alignment to sizeof(int)).

It might be better to introduce PaUtil?_AllocateAlignedMemory( size, alignment ) for larger alignments.

see: http://www.portaudio.com/docs/v19-doxydocs/pa__util_8h.html