Moved FNV hashing into libstd

test hash::fnv::test::bench_compound_1                      ... bench:        12 ns/iter (+/- 1)
test hash::fnv::test::bench_long_str                        ... bench:       816 ns/iter (+/- 12)
test hash::fnv::test::bench_str_of_8_bytes                  ... bench:         0 ns/iter (+/- 0)
test hash::fnv::test::bench_str_over_8_bytes                ... bench:         0 ns/iter (+/- 0)
test hash::fnv::test::bench_str_under_8_bytes               ... bench:         0 ns/iter (+/- 0)
test hash::fnv::test::bench_u64                             ... bench:         0 ns/iter (+/- 0)

vs.

test hash::sip::tests::bench_compound_1                     ... bench:        66 ns/iter (+/- 35)
test hash::sip::tests::bench_long_str                       ... bench:       747 ns/iter (+/- 904)
test hash::sip::tests::bench_str_of_8_bytes                 ... bench:        38 ns/iter (+/- 54)
test hash::sip::tests::bench_str_over_8_bytes               ... bench:        44 ns/iter (+/- 26)
test hash::sip::tests::bench_str_under_8_bytes              ... bench:        36 ns/iter (+/- 13)
test hash::sip::tests::bench_u64                            ... bench:        30 ns/iter (+/- 14)