Added support for signed 64 bit integer value computation into the script engine.
This is required because newer official features require support for bigger numbers inside the scripts.
This also cleans up a lot of messy code and fixes a few issues like script stack corruptions.
Thanks to @aleos89 and everyone who supported me with this.
* Alphabetically sorted includes.
* Updated copyright and license text to match across all files.
* Removed pragma once define in header files in lieu of ifdef guards.
* Fixes#3205.
* Follow up to 801d3ed.
* Resolved some string literals requiring a space.
* Redefine my_bool for MySQL 8.0 or later.
Thanks to @bentheexo and @secretdataz!
