Merge pull request #3469 from mfitzp

Fixed pep8 and merged to master locally
BUG : restore back-compatibility of regisiter_backend

revert back-incompatible change from
8159c817bb41dc0c3d86aa909318eb3e55a64d8f

closes #3439
Merge pull request #3467 from cimarronm/mlab_stride_bugfix

BUG : Bugfix in mlab for strided views of np.arrays
Merge pull request #2900 from bytbox/master

TST : Remove no-longer-necessary KnownFail for python 3.2.

no longer needed, because we are no longer testing 3.2
Merge pull request #3478 from tacaswell/regisiter_backend_compat_fix

BUG : restore back-compatibility of regisiter_backend
Merge pull request #3474 from fariza/change-cursor-inmediately

ENH : call set cursor on zoom/pan toggle
Merge pull request #3501 from cimarronm/text_xytext_bugfix

BUG : Bugfix for text.xytext property
fix winbuild link
remove libpng version probing on windows
Merge pull request #3477 from cimarronm/setupext_check_for_libpng

BLD : Better check for required dependency libpng
BUG : don't use super(self.__class__, self)

Simply remove super and explicitly call the correct base class.

closes #3493
Merge pull request #3495 from tacaswell/super_art3D_fix

BUG : don't use super(self.__class__, self)
Merge pull request #3503 from jbmohler/win_fix_simple

BLD : restore non-searching for libpng on windows
Merge v1.4.x back into master