emacs: Tweak search-buffer naming to search list in reverse order

emacs: Tweak search-buffer naming to search list in reverse order

The complete-string matching of commit
f2ebe3ac446afda9ced6507dc391865464ccdcaa
defeats the substitution of partial search
strings when the user manually types a
long search string that just happens to
partially match a saved search.

For example, typing "tag:inbox and not tag:foo"
should result in "[inbox] and not tag:foo" but
this has been broken since that commit.

As a compromise between this feature and what the
commit was trying to achieve, we now reverse the
saved-searches list before looking for a match.
This happens to work for me, but won't necessarily
work in general.

What we really want is the longest match, but rassoc-if
just gives us the first match. All of this is just about
creating slightly nice search-buffer names. So if anyone
really cares about making the names *even* nicer, then
they could improve this further.