Add fat-arrow lambdas, a more terse version of the Python single-expression lambdas
Fix weird parsing bug--try to parse (x) as a fat-arrow lambda first, since otherwise it will reduce to a "test", and won't get a chance to backtrack.
Some string-modulo formatting got left in libparse.mg, replace with .format
A couple small libparse.mg fixes
Allow decorators to be delimited by semicolons, so they work inside brace blocks
Some minor lexer tweaks
Add conditional expressions
Remove 'syntax' keyword
Couple tweaks to libparse.mg to try and reduce stack blowout
Minor syntax.py cleanups