import ``typo-krn``
import ``letterspace-support.lua`` as ``luaotfload-extralibs.lua``

from the mercurial source: https://bitbucket.org/phg/characterkerning
adapt prefix for imported typo-krn
load extralibs in main file
Merge branch 'characterkerning'
sync with Context as of 2013-05-18
combine make rules for resources files
add fallback for older luatexbase
update dates
Merge pull request #78 from phi-gamma/master

v2.2 / TeX Live 2013