searchidx: don't index Base-85 w/ CRLF endings

searchidx: don't index Base-85 w/ CRLF endings

I encountered a false positive search result from a CRLF message
with a Base-85 patch in it.  It turns out our Base-85 filtering
code didn't account for the possibility of "\r" showing up in
patch messages, so just ignore all trailing spaces (not just
horizontal spaces) in index_diff().

While we're at it, exclude horizontal whitespace and CR
consistently from Base-85-looking quoted text in
index_body_text(), too, since I'm sure there's messages with
CRCRLF in the wild, too...