Fix windows compilation issues

[2shady4u]

Windows didn't want to compile anymore on my end.
Two tiny fixes had to be made to get it working again:

• Changing std::isdigit() to isdigit() (removing the std::) does the trick.

• Checking if WIN32 and/or WIN64 is defined for some reason? 🤔 Solely checking for WIN32 doesn't seem to work for Github Actions. Maybe there's a better way to do this?
  There's seems to be the possibility to check for #ifndef HAVE_STRTOK_R which might be more descriptive?

Cheers!