Sort all hash usage in doc generation

Sort all hash usage in doc generation to enable reproducible generation of output. See https://reproducible-builds.org/ for why this is good.

Some of the added sorts might not be needed.

Without this patch, such diff occurred between builds (in spite of using a fixed PERLHASHSEED value) - this is just a sample from 1000 lines overall diff:

--- old//usr/share/doc/packages/vtk-openmpi2-8.2/doxygen/html/idx_vtk_9.html    2019-06-05 23:51:07.988823111 +0000
+++ new//usr/share/doc/packages/vtk-openmpi2-8.2/doxygen/html/idx_vtk_9.html    2019-06-05 23:51:07.984823098 +0000

-<p>occupies</p><ul>
-<li><a class="el" href="classvtkFixedPointRayCastImage.html" title="helper class for a ray cast image">vtkFixedPointRayCastImage</a> ...
(1)</li>
+<p>occupies (occupied)</p><ul>
+<li><a class="el" href="classvtkPointOccupancyFilter.html" title="produce ...


--- old//usr/share/doc/packages/vtk-openmpi2-8.2/doxygen/html/idx_vtk_13.html   2019-06-05 23:51:06.384817996 +0000
+++ new//usr/share/doc/packages/vtk-openmpi2-8.2/doxygen/html/idx_vtk_13.html   2019-06-05 23:51:06.384817996 +0000

-<p>triangulaion (triangulated, triangulating)</p><ul>
-<li><a class="el" href="classvtkDelaunay2D.html" title="create 2D Delaunay ...
+<p>triangulaion</p><ul>
+<li><a class="el" href="classvtkGreedyTerrainDecimation.html" title="reduce

Topic-rename: reproducible-doc-build