xxHash implementation for Perl

 xxHash is a super fast algorithm that claims to work at speeds close to RAM
 limits. The Crypt::xxHash module provides 32- and 64-bit hash functions. As
 bonus it provides 128-bit hex method.
 .
 This package was inspired by Digest::xxHash, but it includes the fresh C code
 and has some optimisations. Thus all hex methods are implemented in Perl XS.
 Also this module doesn't use Math::Int64 in favor of native 64 bit digits.