Initial Release

Haelwenn (lanodan) Monnier (6):
      extract from utils-extra 42c882a201c30165348b373cc4379b1b65d2169f
      .clang-format authorized_keys.git
      Makefile: add xcd-rgb and install-rgb targets
      README.md: new
      xcd.1: new
      tests: import tests & port to simple POSIX sh