Previously, some modules used BH_<Module> prefix in the names of static
functions (some used just <Module> prefix). Now every static function
should start from lowercase.
I wasn't happy with existing implementation of the IO, so I decided
to change it - as a result there is no longer BH_IOOpen and BH_IOClose
and many IO operations are now optional (behind BH_IOCtl).
Finnally implemented buffered IO and fixed size memory buffer IO.
