[PATCH v2 0/5] Index the content-type of MIME parts

[Todd]

This set of patches allows for queries for like:

Find calendar invites
- mimetype:text/calendar or mimetype:application/ics

Find any image attachments
- mimetype:image

Find all patches
- mimetype:text/x-patch

It is a rework of a previous set of patches that now adds a new
database feature, only available in newly created databases, which
indicates that all of the mime parts are indexed.  Indexing of new
messages on an existing database should work fine as well, but the
feature won't be enabled via upgrade.

Code reviews welcome, I'm not familiar with this code base.

Todd (5):
  Add a failing unit test for indexed mime types
  Add the NOTMUCH_FEATURE_INDEXED_MIMETYPES database feature
  Add indexing for the mimetype term
  Update completions for Emacs and bash
  Update documentation

 NEWS                               | 16 ++++++++++++++++
 completion/notmuch-completion.bash |  2 +-
 doc/man7/notmuch-search-terms.rst  |  6 ++++++
 emacs/notmuch.el                   |  2 +-
 lib/database-private.h             | 15 ++++++++++++---
 lib/database.cc                    | 11 +++++++++--
 lib/index.cc                       |  6 ++++++
 test/T190-multipart.sh             | 32 ++++++++++++++++++++++++++++++++
 8 files changed, 83 insertions(+), 7 deletions(-)

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1.9.1