improvements to oepnvg.xtm library/example

Squashed commit of the following:

commit 7ee68bc827ea8973478266f0c1a48b23a9e4645e
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 14:34:45 2013 +1100

    added updates fir mostly-64bit xtm 2d library

commit 025dc83136d9ee261d59be84d32600089f62105d
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 14:33:32 2013 +1100

    improved buffer munging for xtm.xtm

commit 11deb493d053f017605ff45a3730384aa9804b99
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 12:12:38 2013 +1100

    update openvg example for vg64

commit b65853a609940b0d0e552e848b25427316cac532
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 10:57:18 2013 +1100

    bugfixes for vg paint stuff

commit a39048b580d3db2f10e1e3b5ffb8f594d969febe
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 10:04:04 2013 +1100

    add some more helper functions (triangles and quads)

commit 8fd208e026fe1e616f886196c9e95b6074cea06d
Author: Ben Swift <benjamin.j.swift@gmail.com>
Date:   Mon Oct 21 09:59:00 2013 +1100

    first compiling version of 64-bit openvg lib