Add libOpenMPT

[Wohlstand]

This is a better libModPlug which supports more formats and gives better sound quality. Library is licensed under BSD license. It is developing in same repository as Open ModPlug Tracker project.

https://lib.openmpt.org/libopenmpt/

[Wohlstand]

Library has been added:

It is:

• buildable with CMake
• linkable with example utility
• works with pre-included example utility

But:

• Incompatible with MSVC because of imperfections (won't built even through official project files)
• Heavy library filesize (~18 MB raw static library size)
• Not tested on macOS and not tested with other than GCC/G++ compilers (CLang or Intel CC compilers)

[jaygarcia]

It is a large (and sometimes slow) lib, but can be reduced by removing some non-critical features via compile-time configurations. Just a thought :)