Solidity parser - not polished yet, but usable

First shot at the solidity parser. It generates an AST and infers and checks the types for each expression node.

Mappings and structs are parsed, but not yet integrated into the type system.
If this file will stay in line with the V8 codebase, then we'll it will be an exception for style guidelines.

If it's hard fork, then the style will need fixing up (I see same-line if bodies already).