* arm-tdep.h (enum arm_float_model): New enum.

* arm-tdep.h (enum arm_float_model): New enum.
(struct gdbarch_tdep): Add fp_model.
* arm-tdep.c (arm_gdbarch_init): Set fp_model in tdep.  Defer setting
up floating-point conversions until we know the floating-point model
in use by the inferior.  Don't complain about being unable to
determine the ABI of the inferior when we don't have one.
(arm_extract_return_value): Support different floating-point models.
(arm_store_return_value): Likewise.
* armnbsd-tdep.c (arm_netbsd_aout_init_abi): Set fp_model in tdep to
ARM_FLOAT_SOFT.
(arm_netbsd_elf_init_abi): Set fp_model to ARM_FLOAT_SOFT_VFP.