[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4C 56 am: 1aa02d75f9 -s ours am: 220221d43d -s ours am skip reason: subject contains skip directive skipped: d629acccbf skipped: 4f2fefc067

Change-Id: Idc118c74edfeec75f2852435b2ae4c1f3044e15b