Fix #1615 -- offset is empty.
added test of 'bottom' kwarg in `hist`
fix of issue #1763

The `bottom` that needs to be passed to bar or barh got lost kwarg got
lost in the histogram refactoring.
Merge pull request #1615 from mdboom/offset-empty

Offset is empty with usetex when offset is equal to 1
Merge pull request #1775 from tacaswell/issue_1763

Issue #1763
Fix regression tests.
Fix compilation errors on Launchpad.
Merge remote-tracking branch 'upstream/v1.2.x'

Conflicts:
	lib/matplotlib/axes.py
Fix stackplot test.