Note: formatc.lua was unable to swallow some newer additions to ExprASTNodeType
(specifically `kExprNodeOr = '|'` and probably something else), so all `= …`
were dropped: in any case they only were there in order to not bother updating
viml_pexpr_debug_print_ast_node and since it is now known all nodes which will
be present it is not much of an issue.
It also adds support for kExprLexOr which for some reason was forgotten.
It was only made sure that KLEE test compiles in non-KLEE mode, not that
something works or that KLEE is able to run tests.
First stage: something compiling without klee, but with a buch of dirty
hacks - done.
Second stage: something running under klee, able to emit useful results,
but still using dirty hacks - done.
Third stage: make CMake care about clang argumnets - not done, may be
omitted if proves to be too hard. Not that klee can be run on CI in any
case.
