Solidity scanner taking documentation comments into account

A simple PR, where the scanner will conditionally not skip triple slash comments but instead scan them into comment literal tokens. Accompanying tests also created.

Next TODO step: Use this functionality in the parser.
This is the scanner/lexer, not the parser. This function basically advances the current `m_char` by as many bytes as required to get the next token and then sets the `m_next_token` class member variable.