help tests

[Vladimir Prus <vladimir at codesourcery dot com>]

I'm updating the help.exp testcase for the recently committed changes in help 
output, and I'm starting to wonder if all of those help tests are useful. For 
each command the following is tested:

	- The extact help for the command proper
	- The exact list of subcommands -- for prefix commands and command classes.
	- The epilogue that contains things like:

               Command name abbreviations are allowed if unambiguous

I think it's important to test that "help whatever" produces output, and also 
test some general structure -- like presence of that epilogue. 

On the other hand, I'm not sure that testing for the exact list of subcommands 
is desired. It's not something that can be accidentally broken -- subcommands 
don't get added as side effect of some other change -- they can only appear 
if added explicitly. I also don't think that testing for exact help test for 
the command itself does not make sense -- the help is verbatim string in 
sources -- it can't be accidentally broken and I don't think tests should 
protect against somebody modifying random characters in help strings.

What I think must be tested is that:
	
	1. For every command, class, or prefix command, there's some
	docs.

	2. For classes and prefix commands, help output has the list of
	commands in that class or list of subcommands. But the exact
	list of commands should not be tested.

	3. There's some epilogue, which is appropriate to the type of
	entity we asked help for.

Thoughts? If everybody is fine with it I'll adjust help.exp.

- Volodya