Fix console incorrectly showing on Windows Blender startup in some cases.

The console window is hidden by default, but we need to avoid this when
starting from the command prompt, because it would hide the window you just
typed the command in.

Previously it would check if Blender was started from "explorer.exe" to
determine that, but that wasn't working for application launchers like
Appetizer or Colibri. Instead we now check if the process ID is the same as
the process ID of the console window, which appears to work reliably.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D122