Docs: comments (hash table & beauty fill)
Fix T42927: Triangulate-beauty fails on quads

Regressions since 2.69.
Fix: Never write previews for undo steps.

This may eat quite q bit of mem in the end (though nothing critical),
and icons (material ones e.g.) often ended up out of sync after undo.
Fix triangulating concave quads

Resulting triangles could be pointing in opposing directions.
Fix T42932: Drag&Drop of groups from the outliner was using undefined
event->mval.

Calculating from event->x/y like object drag/drop does works. Also fixed
a missing notifier of the object instancing operator.
Cycles: Add missing entries in the Integrator constructor and some updates
to the XML API.

(Changes from the standalone repo)
Sequencer: Select sideof failed for strips touching the playhead
correct recent cleanup for id-property types
Fix for GPU_materials_free accessing NULL pointer
Quiet warning (harmless)
Correction to set border from render image view

It did not fully support cases when setting border from a cropped render result
and it's not totally clear how it should behave. So for now just do nothing and
inform users about this.
Cycles: Do some logging when motion is detected in the scene
Correction to previous render border commit

Was using wrong bitfield check.
Fix/workaround T42944: Crash adding a shortcut in properties space
cleanup: use const for smallhash & minor edits
Sequener: Move waveform-draw option into view menu

also simplify preview/sequencer checks
PyAPI: disallow assigning members to 'bpy.ops'
Fix T42943: Crash with multiple calls to rna_info.BuildRNAInfo()

Thanks to @nesse for the fix
Flood fill in projection painting does not do bounds checking anymore.

It should now fill the whole mesh with color even if parts of it are
outside the screen - still need to be in fron of the camera though.

Thanks @Campbell for the trick :)
Fix mathutils docstring typos.