Merge pull request #2010 from mdboom/immutable-paths

Allow Paths to be marked as readonly
Merge remote-tracking branch 'upstream/v1.2.x' into HEAD

Conflicts:
	src/_backend_agg.cpp
Merge pull request #2012 from mdboom/texmanager-family-list

texmanager doesn't handle list of names for `font.family`
Merge pull request #2015 from mdboom/usetex-baseline-fixes

Wrong text baseline with usetex.
Merge remote-tracking branch 'upstream/v1.2.x'

Conflicts:
	lib/matplotlib/backend_bases.py
	lib/matplotlib/tests/test_artist.py
	src/_backend_agg.cpp
Merge pull request #2005 from mdboom/saving-animations

Fail to export properly to svg and pdf with interactive paths
Merge pull request #1993 from mdboom/ps-gouraud

PS backend fails to savefig() pcolormesh with gouraud shading
Merge remote-tracking branch 'upstream/v1.2.x'

Conflicts:
	lib/matplotlib/axes.py
Warn when too many figures are opened
Rename rcParam to figure.max_open_warning.  Rewrite warning message.