SH4 instruction set tests.

 Each core instruction has its own set of tests that are assembled into the

 main test executable.

 Note: Since each instruction's tests obviously depends on other

 instructions, its possible for multiple bugs to cancel each other out.

 However the tests are structured as much as possible to prevent this.

 Each test loops repeatedly for a constant number of times (currently 1000)

 to a) ensure that dynamic recompilation kicks in and recompiles the block,

 and b) allow the code to be timed (to a first approximation anyway).