When using the `gnus-search-imap' backend for `gnus-search', there is a
bug in the `gnus-search-run-search' method.  When the search query
begins with parentheses (such as "(OR FROM A FROM B)"), the naive check
for a known IMAP keyword at the beginning fails due to the parenthesis,
and gnus-search adds "TEXT " to the beginning of the query.

Moreover, these are several search keys that are not in
`gnus-search-imap-search-keys'.  These are "new", "not", "old", and
"or".

I include a minimal patch for these problems.

There's another misfeature which I have not attempted to fix that made
debugging the problem much more difficult.  If the result of a query is
not OK, this fact just gets ignored by `gnus-search-run-search' and the
search group is considered empty.  Even after fixing the above problems,
this is a problem when doing a raw search, as one doesn't know whether
the query is bad or if it just does not result in any messages.

Example:

C-u G G "((OR" RET

This results in something like:

577841 BAD Error in IMAP command UID SEARCH: Missing ')' (0.001 + 0.000 secs).

in the process buffer.

Here's a small patch for the first two issues: