:sig
String to_upper(String s)

:params
s : the string to be converted
return value : returns a version of 's' where all lower case characters have been changed into upper case

:see
>string

:content
Returns an upper-case version of `s`.

This function is not yet Unicode-aware.

Related:

- PHP: `strtoupper()`
- JavaScript / Node.js: `String.prototype.toUpperCase()`
