ld-decode profiling notes/performance enhancements

[happycube]

I lost the snippets from the last pass at profiling, so I'll add them here:

at top:

from line_profiler import LineProfiler

in field.decodefield:

        lpf = LineProfiler()
        lpf.add_function(f.refine_linelocs_burst)
        lpf.add_function(f.get_burstlevel)
        lpf.add_function(f.compute_line_bursts)
        lpf.add_function(f.compute_burst_offsets)
        lpf_wrapper = lpf(f.process)

        try:
            lpf_wrapper()
            #f.process()
            lpf.print_stats()
        except (KeyboardInterrupt, SystemExit):
            raise
        except Exception as e:
            raise e

This prints a good number of hotspots, and the upcoming commit based on it will be >=10% faster than current git on NTSC at least.

[happycube]

Good ones for PAL, but the PAL specific TBC code doesn't have many hotspots...

        lpf = LineProfiler()
        lpf.add_function(f.refine_linelocs_pilot)
        lpf.add_function(Field.process)
        lpf.add_function(Field.compute_linelocs)
        lpf_wrapper = lpf(f.process)