[Xastir] Help needed with proj library compatibility

[Tom Russo]

We got a bug report on github that Xastir is using a deprecated API for the
proj.4 library.  A new API (in "proj.h") has been created in proj.5, the old
is deprecated in proj.6, and will be removed in proj.7.  In keeping with the
new normal of racing through major versions every 6 months or so, proj.7 
is due out in 2020. 

I've looked into it, and it turns out that the only uses of proj.4's API 
directly in Xastir source are the result of a hack that was put 
in place to deal with a GDAL/libgeotiff issue, and another place where 
we're including a "contrib" program for shapelib that the main shapelib
distribution has dropped altogether because it's not very useful.

I could use a hand figuring out the best path forward here.

In map_tif.c there is code that conditionally compiles in a substitute
function for GTIFProj4FromLatLong, because some 14 years ago there was
apparently sometimes a problem with this function if one compiled both gdal 
and libgeotiff into Xastir.  The reason for this is that both libraries define
that function, and it was probably possible to compile them in inconsistent 
ways.  The question is whether the hack is still necessary, and
if the presence of both libraries still causes problems in the 
map_tif.c code if the hack were removed.  This will require a lot of 
testing using TIFF maps, and probably on multiple systems to make sure
it's safe to remove.  I will need a lot of help with that, as I have hardly
any time available to test things like this out myself.

If this hack is no longer necessary, the easiest path forward to addressing
the future incompatibility with Proj.6 and Proj.7 will be to remove it 
altogether.  If it is still necessary, then the best path forward might be
to use the GTIFProj4FromLatLong from the upcoming libgeotiff 1.5.0 instead
of the one we have, as the upcoming version has been modified to work with
the new proj.5 API.

I also propose removing "shpproj" from our ancient "internal" shapelib library's
contrib directory, because it is mostly useless and there are better tools
to get the job done (e.g. ogr2ogr, from the GDAL/OGR library).  Is anybody
depending on this program who would object to it disappearing?

-- 
Tom Russo    KM5VY
Tijeras, NM  

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