multibit, fatbit: make _size build-time only

This commit makes mmbit_size() and fatbit_size compile-time only, and
adds a resource limit for very large multibits.

src/nfa/castlecompile.cpp

@@ -49,7 +49,6 @@
 #include "util/graph.h"
 #include "util/make_unique.h"
 #include "util/multibit_build.h"
-#include "util/multibit_internal.h"
 #include "util/report_manager.h"
 #include "util/ue2_containers.h"
 #include "util/verify_types.h"