Delete gdb/testsuite/dg-extract-results.py

Delete gdb/testsuite/dg-extract-results.py

Unfortunately, the Python version of the dg-extract-results.sh script
doesn't produce stable-enough results for GDB.  The test messages
appear to end up alpha sorted (losing the original sequence) and also
sorting changes between runs for some reason.  That may be tolerable
for GCC, but for GDB, it often renders test results diffing between
different revisions unworkable.

Until that is fixed upstream, delete the script from the GDB tree.

testsuite/ChangeLog:
2015-03-09  Pedro Alves  <palves@redhat.com>

	* dg-extract-results.py: Delete.