Merge branch 'develop' into feature/variational-hydro

cmake/PugsDoc.cmake

doc/userdoc.org

src/language/ast/ASTNodeBuiltinFunctionExpressionBuilder.cpp

src/utils/Messenger.cpp

src/utils/PugsMacros.hpp

src/utils/ReproducibleSumMPI.hpp

src/utils/ReproducibleSumUtils.hpp

tests/test_ASTNodeBuiltinFunctionExpressionBuilder.cpp

tests/test_BuiltinFunctionEmbedder.cpp

tests/test_BuiltinFunctionRegister.hpp