allow generating most cdefs for lua

Motivation: maintaining these by hand in kres.lua is tricky, as just
inserting or reordering the structures can do anything and isn't
detected in general.  For example, `rr_array_t::at` has always
"missed a star".

A couple libknot structure fields have apparently changed name since
the old definitions were written; in most cases I renamed them in *.lua.

The file daemon/lua/kres-gen.lua will be regenerated only if explicitly
deleted.  That requires building with debug symbols and gdb on $PATH.