Use ImmutableRecord instead of Record throughout loopy

loopy/codegen/__init__.py

loopy/codegen/control.py

loopy/codegen/result.py

loopy/kernel/__init__.py

loopy/kernel/array.py

loopy/kernel/data.py

loopy/kernel/instruction.py

loopy/library/random123.py

loopy/options.py

loopy/schedule/__init__.py

loopy/symbolic.py

loopy/target/pyopencl_execution.py

loopy/transform/array_buffer_map.py

loopy/transform/subst.py

setup.py