Solidity function AST nodes get documentation attribute
Solidity work for documentation strings

- Still a work in progress

- Parser now properly gets each function's doc comment

- Small changes in the scanner

- Multiline comments are considered
Fixing multiline comment parsing in solidity
Adding solidity natspec comment inside function body
Solidity FunctionDefinition used ASTString shared ptr for docstrings
Solidity natspec docstring test improvements

- Adding a test for docstring being between function signature and
  function body

- Properly checking for exceptions in parsing

- Small parser fix
Simplifying scanning for natspec documentation

- Scanner no longer remembers the last natspect comment until
  a new one is encountered. It remembers it only until the next
  scan()
Moving LiteralScope to Scanner.cpp
Adding natspec comment test being between keyword and signature
simplifying Scanner::reset()
Fix: Storage offset of first struct member should be zero.
Optimizer for literals and identity operations.