Remove/Relicense files with non-Apache 2.0 licenses

[n-eiling]

We have a couple of files that are not licensend under the Apache 2.0 license. We should relicense them or delete them.

As discussed in #939

Some examples:

• https://github.com/VILLASframework/node/blob/master/fpga/thirdparty/rang/rang.hpp
• https://github.com/VILLASframework/node/blob/master/fpga/thirdparty/CLI11/CLI11.hpp

• node/fpga/src/pcimem.c

  Line 9 in 1e0b3d4

  * SPDX-License-Identifier: GPL-2.0-or-later

  
  I think this is not currently used and can be deleted.

• node/tools/hwdef-parse.py

  Line 15 in 1e0b3d4

  SPDX-License-Identifier: GPL-3.0-or-later

  
  This needs to be relicensed or converted to C++ code.

• node/include/villas/kernel/nl-private.h

  Line 5 in 1e0b3d4

  * SPDX-License-Identifier: LGPL-2.1-only

  
  I think this is not currently used and can be deleted.