Warning: +=, -=, *=, etc. on v0.0.13

[behram farrokh thomas mistree]

All,
Just a warning to those of you who may not have paid careful attention
to Ewen's change log for v0.0.13 and are encountering a few weird bugs:

The +=, -=, /=, *= operators may not work for some expressions
correctly. For instance:

this.capPerms +=arguments[s];

turns into

this.capPerms = 7 + arguments[s];

The regular assignment operator should work okay. Be advised! Sorry
for the inconvenience.
-Behram