Miscellaneous syntax improvements

Random ideas for syntax improvements:

• Make the final ";" in an statement list optional, similar to the optional final "," in an expression list:
  • { foo() }
  • { foo(); bar() }
• Make { } indicate a nullary statement lambda, implying the () =>:
  • each(bar, { bas() });
  • This would cause an ambiguity in the parsing of if statements and expressions:
    • if (x) { y() } else { z() }
    • However, since an if expression returning lambdas is currently not valid (the two lambdas are of different incompatible types) the ambiguity could always be resolved in favor of the statement form
• Make the parens around if, while, for and switch optional:
  • if x { y() } else { z() }
  • for x in y { z() }
  • while x { y() }
  • switch x { case y: z() }
  • Looks a bit awkward in the single-statement case, especially with infix expressions:
    • if x y();
    • while x y += z;