Implemented timescale parsing

[christian-krieg]

Hey There,

I was in need to extract the timescale from a VCD file, but didn't find that feature implemented in VCDVCD. So I put in some effort and implemented this feature. I hope you find it useful as well, and it would be cool to see this propagating upstream.

Looking forward to our discussion!

In the following, I listed the changes I made to the VCDVCD class:

• The timescale is parsed into a dictionary VCDVCD::_timescale that holds key/value pairs describing the time scale

• List of keys:

  "timescale": The timescale in seconds (SI unit) "number" : The time number as specified in the VCD file "unit" : The time unit as specified in the VCD file "factor" : The numerical factor derived from the unit

• The functionVCDVCD::get_timescale() returns the dictionary

Cheers!

[cirosantilli]

Thanks for this Christian! I should stop being lazy and add tests. But hey, lazy! XD

One small thing, at f.readline().strip().rstrip() I think strip() already does an rstrip() so rstrip is not needed?