More markings of messages for i18n, with updates to various tests
to pass GETTEXT_POISON tests.

One patch from the original submission dropped due to conflicts
with jk/upload-pack-hook, which is still in flux.

* va/i18n-even-more: (38 commits)
  t5541: become resilient to GETTEXT_POISON
  i18n: branch: mark comment when editing branch description for translation
  i18n: unmark die messages for translation
  i18n: submodule: escape shell variables inside eval_gettext
  i18n: submodule: join strings marked for translation
  i18n: init-db: join message pieces
  i18n: remote: allow translations to reorder message
  i18n: remote: mark URL fallback text for translation
  i18n: standardise messages
  i18n: sequencer: add period to error message
  i18n: merge: change command option help to lowercase
  i18n: merge: mark messages for translation
  i18n: notes: mark options for translation
  i18n: notes: mark strings for translation
  i18n: transport-helper.c: change N_() call to _()
  i18n: bisect: mark strings for translation
  t5523: use test_i18ngrep for negation
  t4153: fix negated test_i18ngrep call
  t9003: become resilient to GETTEXT_POISON
  tests: unpack-trees: update to use test_i18n* functions
  ...