* sparc-tdep.h (struct gdbarch_tdep): Add step_trap member.

* sparc-tdep.h (struct gdbarch_tdep): Add step_trap member.
(sparc_address_from_register): New prototype.
(sparcnbsd_step_trap): New prototype.
* sparc-tdep.c (sparc_address_from_register): Make globally
visible.
(sparc_analyze_control_transfer): Change prototype to accept
`struct gdbarch *' as first argument.  Allow for optional hnadling
for trap instructions.
(sparc_step_trap): New function.
(sparc_software_single_step): Adjust call to
sparc_analyze_control_trabsfer.
(sparc32_gdbarch_init): Initialize TDEP->step_trap.
* sparcnbsd-tdep.c (sparcnbsd_step_trap): New function.
(sparc32nbsd_init_abi): Set TDEP->step_trap.
* sparc64obsd-tdep.c (sparc64obsd_init_abi): Set TDEP->step_trap.
* sparc64nbsd-tdep.c (sparc64nbsd_init_abi): Set TDEP->step_trap.