Patch the Ragel lexer after generating it.

This further increases throughput of the lexer. On MRI this seems to save
around one second or so. It now sits at ~6,8 seconds in the big XML benchmark.

On JRuby, combined with some JIT options and invoke dynamic enabled, this can
reduce the average lexing time to around 3,5 seconds.  Rubinius, also with a
few aggressive JIT options, seems to stick around 9 seocnds.