Case insensitive lookfor()

[Rik]

All,

I chanced upon an issue with the lookfor () command today.  I expected it
to find the exact string I was looking for, but instead it uses search_str
= lower (input_str).  Presumably this new search_str was meant to be
compared against an all lower case version of the help string.  However,
this is not what is in the doc-cache; only the true help text with
capitalization is in the doc-cache.

Example:
get_first_help_sentence ("ls")
ans = List directory contents.
lookfor ("List directory")
<nothing>
lookfor ("ist directory")
ls                  List directory contents.

The lower() call makes it impossible to find certain keywords, often Matlab
ones, which use mixed case such as "UniformOutput".  Offhand, I would vote
for just removing the lower function call.  However, if everyone is really
keen to have case insensitive matching then we could expand doc-cache to
store a lower-case version of all of the help text.  This would double the
current doc-cache size from 1.3 MB to 2.6 MB.

Cheers,
Rik