test framework

[Szabolcs Nagy <nsz@port70.net>]

now that cluts has many tests i was started to
think how to put these into a framework so it's
easy to add new tests

imho it is a tiny bit more convenient than just
writing functions which return nonzero on error

i also added benchmarking support now
(some tests and benchmarks were added from
libc-testsuit and libc-bench)

http://repo.or.cz/w/musl-test.git

the idea of iterative benchmarking until elapsed
time is large enough is from the go testing
package, i'm not sure if this is the right
approach (for the malloc benchmarks it is not)

(makefile is uglier than it should be because i
still haven't fixed my musl-gcc)

finally: i added short int and int division
benchmarks to verify a discussion on irc :)

comments are welome