Cleaned up and updated the test; the code was written with a pre-C99
standard in mind.
Added a get() method into mxs::Buffer to make it easier to use with
non-C++ functions.
maxscale::Buffer is a simple C++ wrapper around GWBUF that allows the
latter to be manipulated like an STL compatible collection.
maxscale::Buffer provides both a const and non-const forward iterator,
using which a non-contiguous GWBUF can be traversed and manipulated.
The iterators can be used with any standard C++ algorithm that accepts
forward iterators.
