This actually fixes a bug with the FitsHDU class where if a FitsHDU is created from non-file-backed HDUList, it fails to properly generate the XINDn keywords because the _hdrLoc/_datLoc attributes of each HDU in the HDUList are not populated.  This fix updates the _hdrLoc/_datLoc attributes of an HDU whenever it's written out to a file (including in-memory file-like objects) which is probably not a bad idea anyways.
This actually fixes a bug with the FitsHDU class where if a FitsHDU is created from non-file-backed HDUList, it fails to properly generate the XINDn keywords because the _hdrLoc/_datLoc attributes of each HDU in the HDUList are not populated.  This fix updates the _hdrLoc/_datLoc attributes of an HDU whenever it's written out to a file (including in-memory file-like objects) which is probably not a bad idea anyways.

git-svn-id: 5305e2c1a78737cf7dd5f8f44e9bbbd00348fde7@1246 ed100bfc-0583-0410-97f2-c26b58777a21

embray/PyFITS,embray/PyFITS,spacetelescope/PyFITS,embray/PyFITS,spacetelescope/PyFITS,embray/PyFITS