Add Iterable.countWithPredicate
Add support for mixed tuples in the compiler
Fix typo
Compiler fixes
Add override
Do not GC during parsing, because there are lots of raw pointers flying around
Add virtual destructors
Stop exiting with status -1; that's illegal
Small GC fixes
Numerous minor changes in the pursuit of an elusive GC bug (still not found).
Less wasteful length calculation in listify
Require higher GC debug level to use weak pointers
Stop using recursion for do_mark, to avoid smashing the stack