v2.8.0

API changes:

• Enclosed the whole project into opensmt namespace.
• Using also directory names when including files.
• Adapted parts of the API of MainSolver to the SMT-LIB 2.6 terminology that uses "assertion stack".

Bug fixes:

• Named terms: do not report error when re-introducing a named term with an already popped name.
• Do not reverse the arguments of XOR terms.

New features:

• Support ":minimal-unsat-cores" option - naive implementation of subset-minimal unsat cores.
• Support ":print-cores-full" option - make the unsat cores strictly agnostic to the ":named" terms.

Build:

• Switch to C++20.
• Bumped minimal CMake version to 3.14.