Fix property init and parent setting in symtab.

The first one was always broken, and managed to not be noticed because I
hadn't gotten to property accesses yet. The second one was broken when the
symtab started using a linked list. It went unnoticed for the same reason.
Whoops! Fix exception bugs from last commit.
Class properties can now be accessed! Fixes #60.

Class property access is done by 'x.y', similar to how methods are accessed.
The only difference is that class properties will tend to be not-callable, so
no () is needed.

The code is a bit rough for now: There's no support for get/set type
restrictions or private/protected/public. I'll touch up oo access when those
arrive.

Finally, tree_oo_call and oo_call in general is now called tree_oo_access and
oo_access, respectively.