[RFC] moving the parser to use flex >=2.5.33' buffer stack manager
the following patch (still a work in progress) moves the parser to use
flex's internal buffer stack to manage the include files removing the
depth limitation of 10 include files (up to the number of available file
handles based on my test in Fedora 10 x86).
it seems to pass all checks from the test suite but is still missing
appropiate handling of cfg->filename and definitely needs more testing
and discussion, specially considering it will require bootstrapping with
flex 2.5.33 or newer.