[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 skipped: 47a6cd0017

Change-Id: I405aba37eeb8d504da27faaa42f4e16878f61746