Speed up post-parse processing

[jgressma]

Improve post processing speed for larger DBC files.

The file used for testing is 7.3M large. Time spent to parse the file went from approx. 72 seconds (v3.2.6) to 0.018 seconds on my i5 machine.

[xR3b0rn]

Ooof, that's nice! I will take a look at this!

Thanks for sharing this!