rebase with upstream release 0.36 (bz #2075939)
    
    Library
    -------
    
    Add the `sexp` prefix to the infix (traditional) query parser. This
    allows specific subqueries to be parsed by the sexp parser (with
    appropropriate quoting). See `notmuch-search-terms(7)` for details.
    [Packaged without `sexp` in Fedora so far.]
    
    Add another heuristic to regexp fields to prevent phrase parsing of
    bracketed sub-expressions.
    
    Command Line Interface
    ----------------------
    
    Envelope from ("From ") headers are now escaped as X-Envelope-From: in
    input to `notmuch-insert`. This prevents creating mbox files when
    calling `notmuch-insert` from e.g. `postfix`.
    
    Python (CFFI) Bindings
    ----------------------
    
    Use the `config_pairs` API in ConfigIterator. This returns all
    matching key-value pairs, not just those that happen to be stored in
    the database.
    
    Documentation
    -------------
    
    Reorganize documention for `notmuch-config`. Add a few links from
    other man pages.
    
    Emacs
    -----
    
    Bind the usual undo key sequences to new command
    "notmuch-tag-undo". This allows transparent undo of tagging
    operations.
    
    Tests
    -----
    
    Fix smime.4 with newer gmime. Unset `XDG_DATA_HOME` and `MAILDIR` for
    tests.