v0.9.4

Changelog

68c02ce feature: expose extract package, previously internal
4b3e9ee feature: use environment in addition to flags to control test options
8916618 interp: API change for Symbols method
d47821b interp: add indexExpr check for reflect.Array
c74d050 interp: added kind to log for typecheck (#910)
d7ede8e interp: added sliceExpr and starExpr
22c63b2 interp: fix array size definition in case of forward declared constant
c0eaab0 interp: fix assignable check
804664c interp: fix type check in constant unary operations
513f5e3 interp: fix type conversion for constant expressions
9520a92 interp: fix type in assign of shift operations