* ppc-tdep.h (struct gdbarch_tdep): Change definition of

* ppc-tdep.h (struct gdbarch_tdep): Change definition of
ppc_fp0_regnum and ppc_fpscr_regnum: if they are -1, then this
processor variant lacks those registers.
(ppc_floating_point_unit_p): Change description to make it clear
that this returns info about the ISA, not the ABI.
* rs6000-tdep.c (ppc_floating_point_unit_p): Decide whether to
return true or false by checking tdep->ppc_fp0_regnum and
tdep->ppc_fpscr_regnum.  The original code replicated the BFD
arch/mach switching done in rs6000_gdbarch_init; it's better to
keep that logic there, and just check the results here.
(rs6000_gdbarch_init): On the E500, set tdep->ppc_fp0_regnum and
tdep->ppc_fpscr_regnum to -1 to indicate that we have no
floating-point registers.
(ppc_supply_fpregset, ppc_collect_fpregset)
(rs6000_push_dummy_call, rs6000_extract_return_value)
(rs6000_store_return_value): Assert that we have floating-point
registers.
(rs6000_dwarf2_stab_reg_to_regnum): Add FIXME.
(rs6000_frame_cache): Don't note the locations at which
floating-point registers were saved if we have no fprs.
* aix-thread.c (supply_fprs, fill_fprs): Assert that we have FP
registers.
(fetch_regs_user_thread, fetch_regs_kernel_thread)
(store_regs_user_thread, store_regs_kernel_thread): Only call
supply_fprs / fill_fprs if we actually have floating-point
registers.
(special_register_p): Check ppc_fpscr_regnum before matching
against it.
(supply_sprs64, supply_sprs32, fill_sprs64, fill_sprs32): Don't
supply / collect fpscr if we don't have it.
* ppc-bdm.c: #include "gdb_assert.h".
(bdm_ppc_fetch_registers, bdm_ppc_store_registers): Assert that we
have floating-point registers, since I can't test this code on
FP-free systems to adapt it.
* ppc-linux-nat.c (ppc_register_u_addr): Don't match against the
fpscr and floating point register numbers if they don't exist.
(fetch_register): Assert that we have floating-point registers
before we reach the code that handles them.
(store_register): Same.  And use tdep instead of calling
gdbarch_tdep again.
(fill_fpregset): Don't try to collect FP registers and fpscr if we
don't have them.
(ppc_linux_sigtramp_cache): Don't record the saved locations of
fprs and fpscr if we don't have them.
(ppc_linux_supply_fpregset): Don't supply fp regs and fpscr if we
don't have them.
* ppcnbsd-nat.c: #include "gdb_assert.h".
(getfpregs_supplies): Assert that we have floating-point registers.
* ppcnbsd-tdep.c (ppcnbsd_supply_fpreg, ppcnbsd_fill_fpreg): Same.
* ppcobsd-tdep.c: #include "gdb_assert.h".
(ppcobsd_supply_gregset, ppcobsd_collect_gregset): Assert that we
have floating-point registers.
* rs6000-nat.c (regmap): Don't match against the fpscr and
floating point register numbers if they don't exist.
(fetch_inferior_registers, store_inferior_registers,
fetch_core_registers): Only fetch / store / supply the
floating-point registers and the fpscr if we have them.
* Makefile.in (ppc-bdm.o, ppc-linux-nat.o, ppcnbsd-nat.o)
(ppcobsd-tdep.o): Update dependencies.