Merge branch 'ab/i18n-fixup' into maint

Merge branch 'ab/i18n-fixup' into maint

* ab/i18n-fixup: (24 commits)
  i18n: use test_i18n{cmp,grep} in t7600, t7607, t7611 and t7811
  i18n: use test_i18n{grep,cmp} in t7508
  i18n: use test_i18ngrep in t7506
  i18n: use test_i18ngrep and test_i18ncmp in t7502
  i18n: use test_i18ngrep in t7501
  i18n: use test_i18ncmp in t7500
  i18n: use test_i18ngrep in t7201
  i18n: use test_i18ncmp and test_i18ngrep in t7102 and t7110
  i18n: use test_i18ncmp and test_i18ngrep in t5541, t6040, t6120, t7004, t7012 and t7060
  i18n: use test_i18ncmp and test_i18ngrep in t3700, t4001 and t4014
  i18n: use test_i18ncmp and test_i18ngrep in t3203, t3501 and t3507
  i18n: use test_i18ngrep in t2020, t2204, t3030, and t3200
  i18n: use test_i18ngrep in lib-httpd and t2019
  i18n: do not overuse C_LOCALE_OUTPUT (grep)
  i18n: use test_i18ncmp in t1200 and t2200
  i18n: .git file is not a human readable message (t5601)
  i18n: do not overuse C_LOCALE_OUTPUT
  i18n: mark init-db messages for translation
  i18n: mark checkout plural warning for translation
  i18n: mark checkout --detach messages for translation
  ...