Each built-in exception is now a type, with base type BaseException.
C exceptions are created by passing a pointer to the exception type to
make an instance of. When raising an exception from the VM, an
instance is created automatically if an exception type is raised (as
opposed to an exception instance).
Exception matching (RT_BINARY_OP_EXCEPTION_MATCH) is now proper.
Handling of parse error changed to match new exceptions.
mp_const_type renamed to mp_type_type for consistency.
Linear table at the moment, to eventually be replaced with a hash table
generated by a preprocessor.
Dynamic table is retained so that builtins can be overridden.
sys.path is not initialized by rt_init(), that's left for platform-specific
startup code. (For example, bare metal port may have some hardcoded defaults,
and let user change sys.path directly; while port for OS with environment
feature can take path from environment). If it's not explicitly initialized,
modules will be imported only from a current directory.
Paul Sokolovsky
Damien George