* mips-tdep.c (mips32_scan_prologue): Add advance declaration.

    * mips-tdep.c (mips32_scan_prologue): Add advance declaration.
        Remove sp as a parameter, compute it internally instead. Move
        prologue scanning limit from heuristic_proc_desc to here.
        (mips16_scan_prologue): Likewise.
        (mips_insn16_frame_cache): Replace call to heuristic_proc_desc
        by call to mips16_scan_prologue.
        (mips_insn32_frame_cache): Replace call to heuristic_proc_desc
        by call to mips32_scan_prologue.
        (heuristic_proc_desc): Remove code that's no longer necessary.
        Update calls to mips16_scan_prologue and mips32_scan_prologue.
        (mips_skip_prologue): Update calls to mips16_scan_prologue
        and mips32_scan_prologue.