Tests for tohtml

This directory provides fairly extensive tests for the tohtml program.

The test needs to run LaTeX to generate some of the images that are
used for complex LaTeX and for figures. This raises several issues;

1) There is a lot of irrelevant output.  To solve this, after "make testing"
   run "make compare" .  That will simply compare the generated output from
   a set of reference data.

2) Some of the data may not compare. This can happen if the process that
   creates some of the image files generates images that are slightly different
   in size.  For example, a recent test produced this output:

File test1/img2.gif differs from reference:
Binary files test1/img2.gif and testref/test1/img2.gif differ
File test1/img3.gif differs from reference:
Binary files test1/img3.gif and testref/test1/img3.gif differ
File test1/node1.html differs from reference:
67c67
< This is an inline <img width=23 height=6 src="img2.gif" alt="Image file">
---
> This is an inline <img width=22 height=6 src="img2.gif" alt="Image file">
75c75
< This is an inline <img width=23 height=6 src="img3.gif" alt="Image file">
---
> This is an inline <img width=22 height=6 src="img3.gif" alt="Image file">

This is not an error - there is a one pixel difference in width of these two
figures, and that can be ignored.