WIP:Merge Wimp_StartTask R0 = 0
The first commit merges the Wimp_StartTask R0 = 0 work in with the latest Wimp. This has a problem, that creating a new thread immediately after Wimp_Initialise causes the OS environment to be filled with rubbish on return to the parent. The second commit fixes this problem.
It builds, soft-loads, and the test programs work.
N.B. In the C test programs quitting the parent before the child causes the machine to freeze