Replace std::regex to improve performance

[DarkoGNU]

SimpleLogo uses std::regex for some operations on std::string. This is fine, but std::regex is pretty slow.

This will be an issue if someone uses SimpleLogo to execute large scripts

Std::regex should be replaced either by a more efficient regex library (like Google's RE2) or by our own algorithms.

Won't fix for now - unless someone needs the performance improvement, this isn't worth fixing

[DarkoGNU]

Mentioned in #2