pick: added support for hg abort This patch isolates abort logic for `hg pick --abort` as `abortpick()`. For independent calls via `hg abort` `hgabortpick()` is created and registered to the state detection API. Results are shown as tests.

. $TESTDIR/testlib/pythonpath.sh

cat >> $HGRCPATH << EOF
[extensions]
docgraph=
EOF