Build fixes for variants pre RISC OS 5
Robert Sprowson authored
Minor fixups as part of univeral !Boot work.
Options no longer ASSERT on International_Help (which is a definition exported by the kernel, rather than a build switch), and instead define a switch which is true for > 3.50.
Non UTF8 supporting case has simple substitutes for Wimp_TextOp.
Legacy_DomainId and LegacyIRQsema no longer cause NULL pointer dereference.
MOVeQ => MOVEQ to placate ObjAsm.

Ursula_RPC version built and used briefly on RISC OS 4.02 host. No other run time testing.

Version 5.22. Tagged as 'Wimp-5_22'
fc22d68f