pyplot.gci: Look first in current axes, not most recently added axes.

This fixes a bug in which the behavior of gci did not match its
docstring, as pointed out by Julien Cornebise.
Merge pull request #1944 from mdboom/cancel-zoom

ValueError exception in drag_zoom (tk backend)
BUG: Fix ValueError: setting an array element with a sequence

This is fixed in the master branch
Merge pull request #2119 from efiring/fix_gci

pyplot.gci: Look first in current axes, not most recently added axes.
Merge pull request #2144 from cgohlke/patch-3

BUG: Fix ValueError: setting an array element with a sequence
Merge remote-tracking branch 'upstream/v1.2.x' into v1.3.x