first draft of the mmap patch series

first draft of the mmap patch series

The purpose of these changes to para_server is to not call
read()/fseek() in the audio format handlers and in vss.c but to use
mmap() instead which should result in less code and should also be
faster and less error-prone.

This first patch implements the basic infrastructure for mmap but
keeps the file pointer so that changes may be merged step by step and
changes the ogg vorbis audio format handler to use the new mapping
of the audio file.

Subsequent patches will change the other audio format handlers and
the virtual streaming system to also use mmap instead of read()/fseek().