meson: Fix license field
Before this commit, the field specified "GPL2+" as license which is wrong on several levels:
- the
license
field should specify a SPDX license identifier (which "GPL2+" is not) - throughout the whole repository multiple licenses are used (not just GPL2 and later)
- the main library code is licensed under the LGPL, version 2.1 and later
Fix this by providing a proper SPDX identifier:
- The main library code is licensed under the LGPL, version 2.1 and later
- The tests are licensed under either the Apache (v2) license or GPL (v2 or later)