Switch to subclassing GPS and manipulating a global pointer. Update the test program so that it works again.
git-svn-id: https://arducopter.googlecode.com/svn/trunk@673 f9c3cf11-9bcb-44bc-f272-b75c42450872
Note that this is currently disabled as changes need to be made to APM to support it.
Tested with MTK, u-blox and SiRF GPS'.
git-svn-id: https://arducopter.googlecode.com/svn/trunk@671 f9c3cf11-9bcb-44bc-f272-b75c42450872