[Xastir] Xastir Release 2.1.2

[Curt Mills]

This release of Xastir implements the following changes:

- National Weather Service shapefile script updated, dbfawk files added.

- Compilation errors in OS X earlier than 10.6 fixed.

- Tiger WMS server maps added.

- A new set of National Map .geo files replaces those that referenced WMS
products that have gone off-line since the last release.

- GDAL and OGR support removed.

- Xastir builds are now reproducible (builds no longer contain the build
date and time).

- Deprecated GraphicsMagick and ImageMagick function calls replaced with
new API.

- Download of tiled maps is now handled by a download manager running in a
separate thread, dramatically improving map update speed.

- Obsolete interface to old Tiger/Line map server removed (the server went
down years ago).

- OpenTrac decoding support removed.

- Support for the old PocketAPRS (PalmOS based APRS) map format has been
removed.  Users of these old map types should transition to a more modern
format.

- Xastir sources no longer contains a copy of an old version of shapelib
source.  Shapelib support must now always be provided by an external
library.

- The embryonic "Xastir-qt" project has been moved to a separate repository.

- "Xastir -V" will now cause Xastir to report its version number (with git
sha-1 hash appended if built from a git clone) and exit.

- Support for many additional satellite navigation (GNSS) receivers has
been added to the existing GPS support.  Prior to this release, only NMEA
sentences starting with $GP were recognized.

- Many compilation warnings from recent GCC and Clang compilers have been
eliminated, resulting in a cleaner build.

- Our Makefiles now default to "silent rules" to reduce uninteresting
output during compliation.  The old, noisier behavior may be invoked by
adding "V=1" to the "make" line at build time.

- The configure summary now shows the status of its probe for Xpm libraries
under "Xpm / Snapshots".

Xastir web pages: http://xastir.org
Xastir Code: https://github.com/Xastir/Xastir