Prepare for implementing second backend: add build-system support for different backends, including stub support.
"0" -> nullptr; "0" -> false and "1" -> true.

For code readability and warningless builds.
Add "default" branches to switches.

--warnings.
Fix minor GCC-compatibility issues.
Do not use "enum class" with ModField.

It is used as a bitfield; and GCC prohibits using non-integrals
(including enum class, which is AFAIK wrong) with bitfields.
Use Fcast<> to cast pointers-to-functions.
Fix/handle attaching NULL modules to the processor core.
Updated CMake templates.

Also updated uXray checkout with the same changes.
Merge branch 'jit_unification'