Convert i386 target to generic dummy frames.

Convert i386 target to generic dummy frames.
* i386-tdep.c: Include "symfile.h".
(i386_frameless_signal_p): Consider a function to be frameless if
the pc points at the first instruction of the function.
(i386_frame_chain): Handle (generic) call dummies.
(i386_frame_saved_pc): Likewise.
(i386_frame_init_saved_regs): Remove code dealing with call
dummies on the stack.
(i386_push_dummy_frame): Removed.
(i386_call_dummy_words): Removed.
(i386_fix_call_dummy): Removed.
(i386_push_return_address): New function.
(i386_do_pop_frame): Renamed from i386_pop_frame.  Add FRAME
parameter, and don't call get_current_frame.
(i386_pop_frame): New function.
(i386_gdbarch_init): Set use_generic_dummy_frames to 1, set
call_dummy_location to AT_ENTRY_POINT, set call_dummy_address to
entry_point_address, set call_dummy_breakpoint_offset to 0, set
call_dummy_length to 0, set call_dummy_words to NULL, set
sizeof_call_dummy_words to 0, set fix_call_dummy to
generic_fix_call_dummy, set pc_in_call_dummy to
pc_in_call_dummy_at_entry_point, set push_dummy_frame to
generic_push_dummy_frame, set push_return_address to
i386_push_return_address and set frame_chain_valid to
generic_file_frame_chain_valid.