Skewed: pick "base" uniformly from range [0,max_log] and then return "base" random bits. The effect is to pick a number in the range [0,2^max_log-1]

Return a mutable char* pointing to a string's internal buffer, which may not be null-terminated. Writing through this pointer will modify the string.

We provide non-explicit singleton constructors so users can pass in a "const char*" or a "std::string" wherever a "StringPiece" is expected.

Replaces any occurrence of the characters in 'remove' with the character 'replacewith'.