Only include xapian.h in one place, so we can have consistent options.
With that in place, we can enable C++ move semantics.
We don't do anything with that yet, but we check in the meson.build file
to see if we have the required xapian version.
Xapian supports an "ngrams" option to help with languages/scripts
without explicit wordbreaks, such as Chinese / Japanese / Korean.
Add some plumbing for supporting this in mu as well. Experimental for
now.
When passing messages to mu, often we got a (parsed from string)
message-sexp from the message document; then appended some more
properties ("build_message_sexp").
Instead, we can do it in terms of the strings; this is _a little_
inelegant, but also much faster; compare:
(base)
[mu4e] Found 500 matching messages; 0 hidden; search: 1298.0 ms (2.60 ms/msg); render: 642.1 ms (1.28 ms/msg)
(with temp-file optimization (earlier commit)
[mu4e] Found 500 matching messages; 0 hidden; search: 1152.7 ms (2.31 ms/msg); render: 270.1 ms (0.54 ms/msg)
(with temp file optimize _and_ the string opt (this commit)
[mu4e] Found 500 matching messages; 0 hidden; search: 266.0 ms (0.53 ms/msg); render: 199.7 ms (0.40 ms/msg)
It can be faster to feed big mu -> mu4e data, such as contacts are
message headers through a temp-file instead directly though stdout;
implement this, and add the server parameter --allow-temp-file.
Implement this the "contacts" and "find" commands.
For expanding shell options (with expand_path / wordexp)
Note that e.g. in zsh: --maildir=~/Maildir is handled (program receives
--maildir=/home/user/Maildir) but e.g. bash does not do that, and the
program receives the literal '~/Maildir'
We expanded this in mu earlier, so let's do that again.
We were dumping the HTML-parts as-is in the Xapian indexer; however,
it's better to remove the html decoration first, and just pass the text.
We use the new built-in html->text scraper for that.
