This is a cumulative patch that adds the s390x LuaJIT implementation
by @ketank-new, @mundaym and @niravthakkar and others. It contains all
their contributions squashed together, plus minor stylistic cleanups.
It passes all the tests from LuaJIT-test-cleanup, except for
contents.lua, which fails on x86_64 as well.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
