Import ICU 53.1
srtest: return int from main()
icu: fully autotool build scripts

This updates the icu build to use automake and libtool

Compared to the original icu configure.ac the configuration has been
greatly simplified, by cleaning out lots of checks that seem to be
for old systems and compiler problems that hopefully aren't a real
issue any more.
udata: allow apps to handle ICU data loading/caching