bug#1976: 23.0.50; PC-do-completion should fix case if possible

[Stefan Monnier]

> My 2007-10-03 attempt to get this patch applied got no further than RMS's
> request for someone to DTRT.  It took several hours of my time to debug and
> test, and the bug still bites me every time I re-install, so PLEASE could
> someone apply it?  Thanks.

BTW, the default completion in Emacs-23 is very close to
partial-completion-mode.  More to the point, if you remove `basic' from
`completion-styles', it should be pretty much identical except for the
following known differences:
- no <foo.h> style completion for file names.
- M-x lch TAB doesn't know how to expand to `list-command-history'.
And even if you don't remove `basic', the behavior is fairly close.
Also it should fix the problem you're reporting and provides
a few improvements.

Since partial-completion-mode is slated for obsolescence (tho not
marked obsolete yet), I'm interested to hear if you find some other
missing feature.


        Stefan