Minor hotfixes (mostly gcc build fixes)

kernel/select.cc

@@ -22,6 +22,8 @@
 #include <string.h>
 #include <fnmatch.h>
 
+using RTLIL::id2cstr;
+
 static std::vector<RTLIL::Selection> work_stack;
 
 static bool match_ids(RTLIL::IdString id, std::string pattern)

kernel/show.cc

@@ -23,6 +23,8 @@
 #include <string.h>
 #include <dirent.h>
 
+using RTLIL::id2cstr;
+
 #undef CLUSTER_CELLS_AND_PORTBOXES
 
 struct ShowWorker

libs/subcircuit/subcircuit.cc

@@ -1274,6 +1274,10 @@ class SubCircuit::SolverWorker
 			const std::string &graphId = graph_it.first;
 			const auto &graph = graph_it.second.graph;
 			int node2 = adj_it.first;
+
+			if (node1 == node2)
+				continue;
+
 			NodeSet pair(graphId, node1, node2);
 
 			if (usedPairs.count(pair) > 0)

passes/opt/opt_muxtree.cc

@@ -27,6 +27,8 @@
 #include <stdio.h>
 #include <set>
 
+using RTLIL::id2cstr;
+
 struct OptMuxtreeWorker
 {
 	RTLIL::Design *design;

passes/opt/opt_rmunused.cc

@@ -27,6 +27,8 @@
 #include <stdio.h>
 #include <set>
 
+using RTLIL::id2cstr;
+
 static CellTypes ct;
 
 static void rmunused_module_cells(RTLIL::Module *module)