Fix a grwl deadlock in the repl

Well not sure if it's a deadlock; I think we try to
re-entrantly acquire the codegen lock, which then
confuses it later?

src/codegen/irgen/hooks.cpp

@@ -240,6 +240,9 @@ CompiledFunction* compileFunction(CLFunction* f, FunctionSpecialization* spec, E
 }
 
 void compileAndRunModule(AST_Module* m, BoxedModule* bm) {
+    CompiledFunction* cf;
+
+    { // scope for limiting the locked region:
         LOCK_REGION(codegen_rwlock.asWrite());
 
         Timer _t("for compileModule()");
@@ -256,10 +259,9 @@ void compileAndRunModule(AST_Module* m, BoxedModule* bm) {
 
         EffortLevel::EffortLevel effort = initialEffort();
 
-    CompiledFunction* cf = compileFunction(cl_f, new FunctionSpecialization(VOID), effort, NULL);
+        cf = compileFunction(cl_f, new FunctionSpecialization(VOID), effort, NULL);
         assert(cf->clfunc->versions.size());
-
-    _t.end();
+    }
 
     if (cf->is_interpreted)
         interpretFunction(cf->func, 0, NULL, NULL, NULL, NULL, NULL);