Update OpenOCD to 0.7.0

Also get rid of the patch that no longer applies cleanly. It used to do
two things.

1) Remove the -gstabs compiler argument because it wasn't supported on
clang. This has been changed upstream to first check whether the
argument is supported or not.

2) Remove the ccache wrapper. There's an environment variable to control
this behaviour, so use this instead of patching.