lib: str_sanitize*() max_len parameter renamed to max_bytes to describe it more accurately.

str_sanitize*(): Don't crash if max_len is less than 3. str_sanitize(): If there's nothing to sanitize, don't bother allocating memory, just return the input string. Also allow NULL as input. --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Added string sanitization functions. --HG-- branch : HEAD