Patch for HFA no-data value support

[bclaywell]

Enclosed is a patch against the 1.4.0 HFA driver source implementing no-data value support. Only partial BASEDATA support in HFAField::SetInstValue() has been implemented to support this, due to time crunch issues on my end; specifically, only 1x1 BASEDATA arrays of type double are handled. Setting and retrieving the no-data value has been tested and verified in at least simple cases to work correctly; the HFA statistics generation routines correctly honor the set no-data value; and gdalinfo correctly reports the set no-data value.

[warmerdam]

Mateusz,

Could you incorporate this patch in trunk when time permits.

Be quite careful with the basedata portion of the patch (in hfafield.cpp) as I believe there has been other work in this area already recently.

I'm too chicken to incorporate this feature improvement in branches/1.4.

The HFA script(s) should be extended to test the new nodata support.

[Mateusz Łoskot]

Patch applied to trunk along with NoData read/write tests in hfa.py (r13278)