Log Message:
neomutt: update to 20200417.

2020-04-17  Richard Russon  <rich@flatcap.org>
* Features
  - Fluid layout for Compose Screen, see: https://vimeo.com/407231157
  - Trivial Database (TDB) header cache backend
  - RocksDB header cache backend
  - Add <sidebar-first> and <sidebar-last> functions
* Bug Fixes
  - add error for CLI empty emails
  - Allow spaces and square brackets in paths
  - browser: fix hidden mailboxes
  - fix initial email display
  - notmuch: fix time window search.
  - fix resize bugs
  - notmuch: fix entire-thread: update current email pointer
  - sidebar: support indenting and shortening of names
  - Handle variables inside backticks in sidebar_whitelist
  - browser: fix mask regex error reporting
* Translations
  - 100.00% Lithuanian
  - 98.88% Chinese (simplified)
* Build
  - Use regexes for common parsing tasks: urls, dates
  - Add configure option `--pcre2` -- Enable PCRE2 regular expressions
  - Add configure option `--tdb` -- Use TDB for the header cache
  - Add configure option `--rocksdb` -- Use RocksDB for the header cache
  - Create libstore (key/value backends)
  - Update to latest autosetup
  - Update to latest acutest.h
  - Rename `doc/` directory to `docs/`
  - make: fix location of .Po dependency files
  - Change libcompress to be more universal
  - Fix test fails on х32
  - fix uidvalidity to unsigned 32-bit int
* Code
  - Increase test coverage
  - Fix memory leaks
  - Fix null checks
* Upstream
  - Buffer refactoring
  - Fix use-after-free in mutt_str_replace()
  - Clarify PGP Pseudo-header S<id> duration
  - Try to respect MUTT_QUIET for IMAP contexts too
  - Limit recurse depth when parsing mime messages