The includes should make more sense now and not just happen to compile
due to headers included from other headers.
Used a modified version of IWYU. Modifications were to attribute int8_t
and so on to stdint.h instead of sys/types.h and immintrin.h instead of
more specific headers.
include-what-you-use 0.7 (git:b70df35)
based on clang version 3.9.0 (trunk 264728)
Add md5 through extras/libmd5 taken from HM with BSD license. It's
implemented as a generic strategy using the same interface as checksum,
so we can write a SIMD version if it seems necessary.
