Base: Add license manager core code.

Used for license checking and management for prebuilt mex files which
are included in the Psychtoolbox distribution and require paid software
licensing on target platforms like Octave and Matlab on macOS and
Windows. Uses Cryptlex as license management provider, and their
LexActivator SDK and client libraries. See: https://cryptlex.com

This code is implemented and currently used on behalf of Psychtoolbox
commercial host company, the Medical Innovations Incubator GmbH, in
Tübingen, Germany. Website: https://psychtoolbox.net

Any questions wrt. the software licensing should be directed to them
under the following current address, as of November 2024:

Medical Innovations Incubator GmbH
Eisenbahnstr. 63
72070 Tübingen
Germany

Commercial register: HRB 751684
Register court: Local court Stuttgart, Germany
Contact E-Mail address for inquiries: [email protected]

Signed-off-by: Mario Kleiner <[email protected]>