devel/gps: Upgrade to version 5.0.1

Originally this was an attempt to upgrade version 5.0.0 to version
5.1-RELEASE or even 5.2-DEVELOPMENT, but it turns out that those
versions require a GNAT Ada compiler based on gcc 4.7, which hasn't
had its first release yet.  This is mainly due to an change in the
project management API, but using the 4.7 source files fail to
compile due to the new SPARK restrictions.  Therefore GPS must
remain at 5.0.x until such time as GNAT-AUX is based on gcc 4.7.

This is a bug fix release.
The list of bug fixes is unknown, but it's confirmed the bug on the
project dialog, library tab has been fixed and thus those patches
are removed.

The Makefile was updated to allow GPS users to take advantage of
the numerous Python scripts, the Python console, and the python-GTK
bindings.  The option is present, but it has been removed from the
option list because the pkgsrc version of Python cause GPS to core
dump due to missing symbols in their dynamically-loaded libraries.
Version 2.6 and version 2.7 were both tested, and fail in different
ways.  For comparison, the FreeBSD version of GPS builds and operates
fine with Python 2.7, although at times similar "undefined symbol"
messages appear it that error log.  Once the issues with Python are
fixed, this new "python" option in options.mk will be re-enabled.

(marino)