{array.c,bloom.h,bloom.c,memcmp.h,vector.c} Use `size_t` and casting …

[SamuelMarks]

…to resolve some compiler warnings

I like your project concept. So trying to contribute a little bit.

Took this list of warnings and tried to resolve a bunch of them: https://raw.githubusercontent.com/Barro/compiler-warnings/master/clang/warnings-clang-8.txt

…still more to do but sending a PR to see your appetite for such a PR