[geary] (23 commits) ...Merge branch 'letorbi/gmime-3' into 'mainline'

[Michael Gratton <mjog src gnome org>]

Summary of changes:

  1aac6f2... Change GMime dependency from 2.6.17 to 3.2.4
  6a34a61... Remove custom gmime-2.6 bindings
  9eb265b... Update dependencies for CI
  ea646d7... Merge branch 'mainline' into letorbi/gmime-3
  be380b1... Use UTF8_CHARSET for methods that require one; Remove unuse
  660cf37... Clean up and fix setting of message headers
  cc396d4... Fix some code style issues
  c6be77b... Remove last occurences of GMime 2.6
  619b6fb... Merge branch 'mainline' into letorbi/gmime-3
  d98755d... Create new GMime.Part instances with an explicit MIME-type
  132daf5... Restore code to set reply-to header
  e624ab4... Use default format- and parser-options instead of creating 
  5069556... Flush sinks of GMime filter streams
  82c2b36... Make mailbox-address tests pass
  b0df4d5... Return raw but unfolded header values (fixes message-test)
  c0e8f71... Allow addresses without domains (fixes disabled mailbox-add
  4677f4f... Check if header exists before reading value
  793f40f... Set default parser options directly after init
  4374294... Remove redundant call to set the GMime.Parser format; Add s
  ca2bab0... Re-activate and improve prepare_header_text_part() test
  7da9ee1... Fix undefined variable error
  77d44d4... Merge branch 'mainline' into letorbi/gmime-3
  ba3b91f... Merge branch 'letorbi/gmime-3' into 'mainline'