(TARGET_FRW): Add note saying this option is deprecated.

(TARGET_FRW): Add note saying this option is deprecated.

(TARGET_FLAT): Renamed from TARGET_FRW_COMPAT.
(TARGET_SWITCHES): Delete references to -mfrw, -mfrw-compat.  Add -mflat.
(CONDITIONAL_REGISTER_USAGE): If -mflat, fix %i7, rename "%fp"
to "%i7", and make %g7 a global_reg.
(FRAME_POINTER_REQUIRED): Handle -mflat.
(INITIAL_FRAME_POINTER_OFFSET): Likewise.
(ARG_POINTER_REGNUM): Explicitly say it's the frame pointer.
(LEAF_REGISTERS): Make %g7 not a leaf register.
(leaf_reg_backmap): Delete.
(LEAF_REG_BACKMAP): Likewise.
(FUNCTION_PROLOGUE): Handle -mflat.
(FUNCTION_EPILOGUE): Likewise.
(DELAY_SLOTS_FOR_EPILOGUE): Likewise.
(ELIGIBLE_FOR_EPILOGUE_DELAY): Likewise.

From-SVN: r7259