If you set the option to save-before-run you cannot run
a read-only file because the save is done before the
test to see whether it has been modified.
If the save option is not set you get a confusing error
message and a potentially dangerous action if you
decide not to save.
If you attempt to run while editing an HTML file it is
treated as though it were a python script.
When editing an HTML help page there is no easy way of
displaying it to see what it looks like.
This patch corrects these problems.