Rework PowerPC exceptions model to make it more versatile:
* don't use exception vectors as the exception number.
  Use vectors numbers as defined in the PowerPC embedded specification instead
  and extend this model to cover all emulated PowerPC variants exceptions.
* add some missing exceptions definitions, from PowerPC 2.04 specification
  and actual PowerPC implementations.
* add code provision for hypervisor exceptions handling.
* define exception vectors and prefix in CPUPPCState to emulate BookE exception
  vectors without any hacks.
* define per CPU model valid exception vectors.
* handle all known exceptions in user-mode only emulations.
* fix hardware interrupts priorities in most cases.
* change RET_EXCP macros name into GEN_EXCP as they don't return.
* do not stop translation on most instructions that are not defined as
  context-synchronizing in PowerPC specification.
* fix PowerPC 64 jump targets and link register update when in 32 bits mode.
* Fix PowerPC 464 and 464F definitions.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3261 c046a42c-6fe2-441c-8c8c-71466251a162
