Miscellaneous v6-related updates
Ben Avison authored
Detail:
 * Stopped calling the broken abort fixup code when running under VMSAv6.
   Might be desirable to update it, possibly farmed out to a separate module -
   still need to think about this.
 * Unaligned load optimisations can now be disabled by the global NoUnaligned
   flag for testing purposes.
 * Extended OS_ReadUnsigned to permit reading of 64-bit unsigned integers.
   See Docs.ReadUnsigned for more details. Also sped it up by using MLA
   (or UMLAL) for most digits rather than repeated addition.
 * Bugfix is OS_GSRead: an uninitialised r0 was being passed to
   OS_ReadUnsigned, causing undesirable effects on rare occasions.
Admin:
  Tested on a rev B7 beagleboard.

Version 5.35, 4.79.2.98.2.8. Tagged as 'Kernel-5_35-4_79_2_98_2_8'
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