dwarf2cfi: Introduce dw_trace_info.

dwarf2cfi: Introduce dw_trace_info.

This patch only introduces the structure definition and adjusts
the existing routines to use the new cur_trace global to access
the variables that were moved into the structure.

        * dwarf2cfi.c (dw_trace_info): New.
        (dw_label_info): New.
        (cie_return_save): New.
        (cur_trace): New.
        (queued_args_size): Rename from args_size.  Update all users.
        (cfa_store, cfa_temp, regs_saved_in_regs): Remove.
        (def_cfa_1): Use cur_trace instead of cfa_*.
        (dwarf2out_stack_adjust, record_reg_saved_in_reg): Likewise.
        (clobbers_queued_reg_save, reg_saved_in): Likewise.
        (dwarf2out_frame_debug_expr): Likewise.
        (create_cie_data): Split out from ...
        (execute_dwarf2_frame): ... here.  Initialize cur_trace.

From-SVN: r176704