icu4c: Refactor additional locales

Move locales not supported by the current ICU version to local makefiles
This completely separates our additions, preventing future merge conflicts

Change-Id: I9deec28d52c07d04bb153b5b2f19173a900689ff
icu4c: Add Luxembourgish ICU files (converted from CLDR v26)

Change-Id: I975f25bb72831fa0e4f8c9523b9c9c256e2d0b39