A collection of small-size fixes, from a couple of rabbit holes I've been diving down.
- "Use correct access permissions during ROM decompression" hits a code path which isn't currently used
- "PMP LogOp_MapOut fixes" is mainly an optimisation
- "Fix stack imbalance in DA release" could definitely be hit by user code
- "Fixes for zero-size PMPs" isn't likely to be directly hit by user code, but was actually found while releasing a PMP DA
- "OS_Byte 19 fixes" is mainly for ticket 424 https://www.riscosopen.org/tracker/tickets/424
- "Be more forgiving of GraphicsV init failures" is a kernel-side counterpoint to RiscOS/Sources/Video/HWSupport/OMAPVideo!3 (merged). Although the new OMAPVideo will (mostly) solve the issue on OMAP3, modifying the kernel will help out any other platforms that run into similar problems.