Change the layout of the PowerPC E500 raw register cache to allow

Change the layout of the PowerPC E500 raw register cache to allow
the lower 32-bit halves of the GPRS to be their own raw registers,
not pseudoregisters.
* ppc-tdep.h (struct gdbarch_tdep): Remove ppc_gprs_pseudo_p flag;
add ppc_ev0_upper_regnum flag.
* rs6000-tdep.c: #include "reggroups.h".
(spe_register_p): Recognize the ev upper half registers as SPE
registers.
(init_sim_regno_table): Build gdb->sim mappings for the upper-half
registers.
(e500_move_ev_register): New function.
(e500_pseudo_register_read, e500_pseudo_register_write): The 'ev'
vector registers are the pseudo-registers now, formed by splicing
together the gprs and the upper-half registers.
(e500_register_reggroup_p): New function.
(P): Macro deleted.
(P8, A4): New macro.
(PPC_EV_REGS, PPC_GPRS_PSEUDO_REGS): Macros deleted.
(PPC_SPE_GP_REGS, PPC_SPE_UPPER_GP_REGS, PPC_EV_PSEUDO_REGS): New
macros.
(registers_e500): Rearrange register set so that the raw register
set contains 32-bit GPRs and upper-half registers, and the SPE
vector registers become pseudo-registers.
(rs6000_gdbarch_init): Don't initialize tdep->ppc_gprs_pseudo_p;
it has been deleted.  Initialize ppc_ev0_upper_regnum.  Many other
register numbers are now the same for the E500 as they are for
other PowerPC variants.  Register e500_register_reggroup_p as the
register group function for the E500.
* Makefile.in (rs6000-tdep.o): Update dependencies.

Adapt PPC E500 native support to the new raw regcache layout.
* ppc-linux-nat.c (struct gdb_evrregset_t): Doc fixes.
(read_spliced_spe_reg, write_spliced_spe_reg): Deleted.
(fetch_spe_register, store_spe_register): Handle fetching/storing
all the SPE registers at once, if regno == -1.  These now take
over the job of fetch_spe_registers and store_spe_registers.
(fetch_spe_registers, store_spe_registers): Deleted.
(fetch_ppc_registers, store_ppc_registers): Fetch/store gprs
unconditionally; they're always raw.  Fetch/store SPE upper half
registers, if present, instead of ev registers.
(fetch_register, store_register): Remove sanity checks: gprs are
never pseudo-registers now, so we never need to even mention any
registers that are ever pseudoregisters.