Method String.normalize_space()

Method normalize_space: string normalize_space(string s, string|void whitespace)
Parameter s: Is returned after white space in it has been normalised. White space is normalised by stripping leading and trailing white space and replacing sequences of white space characters with a single space.
Parameter whitespace: Defines what is considered to be white space eligible for normalisation. It has a default value that starts with " \t\r\n\v\f" and in addition to that contains all whitespace characters part of Unicode. The first character denotes the character for replacing whitespace sequences.
Note: Trailing and leading whitespace around \r and \n characters is stripped as well (only useful if they're not in the whitespace set).
Note: This function is a lot faster with just one argument (i.e. the builtin whitespace set has an optimised code path).