new class: TreeDifferenceFilter

This new filter allows us to compare two vtkTrees.

Change-Id: I6468973b92bc9c993efc741d453f0d5aee37b14e
Fix some logic errors

In RequestData, we need to initialize the EdgeMap in the case where
the user did not specify an IdArrayName.  Previously, a copy/paste error
had us initializing the VertexMap twice.

In ComputeDifferences, use the VertexMap when the comparison array
belongs to the VertexData.  Previously, we used the EdgeMap
unconditionally.

Change-Id: I9fb9dfd27041f55bf6c6f8700e073651353e8635
Backport using Tcl_GetErrorLine with Tcl8.6

Change-Id: I82150869b1f473b6c56e56167aece5e73089d7bb
Let macro find TclTk version 8.6

Change-Id: Iaf16f371c9e8767bd85f155e863aa92229234abe
Update the TclTk internal files for 8.6

Change-Id: I2af0a113a8080fa17fb8feb0114040739af849bb
Merge release-tcl86_update into master-tcl86_update

Change-Id: I259da74b8cfe4bca3e6d616caac2464f2b46455a
address Gerrit feedback

* PrintSelf now outputs the algorithm parameters
* use vtkDataArray internally instead of vtkDoubleArray.
* comment change: ascend towards the root of the tree
  (was previously descend)

Change-Id: If70a6ccdbc9377c822fa1d130fb494ea56ce7e3c
silence warnings

Eliminate "unreferenced formal parameter" warnings revealed by
CDash@Home

Change-Id: I5628673487d60e7d021680696d342e032b6fb581
COMP: Add missing "using" keyword to the keyword rule.

This issue was discovered when "using" appeared within an inline function.

Change-Id: Iad9f52bd0f0e682c8694a493a39950a167e09484
Merge topic 'compare_trees' into master

d4281ea9 silence warnings
572a52b8 address Gerrit feedback
96c795bf Fix some logic errors
3ef7f687 new class: TreeDifferenceFilter
Merge topic 'vtkparse-missing-keyword' into master

a1db9227 COMP: Add missing "using" keyword to the keyword rule.
Merge topic 'gl2ps-size-factors' into pv-master

6643a93 Restore ability to scale gl2ps linewidth/pointsize.
Merge remote-tracking branch 'pvvtk/pv-master' into HEAD

Change-Id: I2018497d09ed93131c356495579a2d7dd3e7cd45
Merge topic 'master-tcl86_update' into master

1b1d6172 Merge release-tcl86_update into master-tcl86_update
4eed633d Update the TclTk internal files for 8.6
58467677 Let macro find TclTk version 8.6
df4daa34 Backport using Tcl_GetErrorLine with Tcl8.6