Rework the memory load/store:
- Unify load/store functions for 32-bit and 64-bit CPU
- Don't swap values twice for bit-reverse load/store functions
  in little endian mode.
- On a 64-bit CPU in 32-bit mode, do the address truncation for
  address computation instead of every load store. Truncate the
  address when incrementing the address (if needed)
- Cache writes to access_types.
- Add a few missing calls to gen_set_access_type()
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5949 c046a42c-6fe2-441c-8c8c-71466251a162