Bug 1302142 - Accept any value as valid input for MIteratorStart. r=jandem

js/src/jit-test/tests/ion/for-in-iterator-1.js

js/src/jit/BaselineIC.cpp

js/src/jit/CodeGenerator.cpp

js/src/jit/CodeGenerator.h

js/src/jit/Lowering.cpp

js/src/jit/MIR.h

js/src/jit/TypePolicy.cpp

js/src/jit/shared/LIR-shared.h

js/src/jit/shared/LOpcodes-shared.h

js/src/jsiter.cpp

js/src/jsiter.h

js/src/vm/Interpreter.cpp