add mrb_gv_remove(); untested

include/mruby/variable.h

@@ -53,6 +53,7 @@ mrb_value mrb_mod_constants(mrb_state *mrb, mrb_value mod);
 mrb_value mrb_f_global_variables(mrb_state *mrb, mrb_value self);
 mrb_value mrb_gv_get(mrb_state *mrb, mrb_sym sym);
 void mrb_gv_set(mrb_state *mrb, mrb_sym sym, mrb_value val);
+void mrb_gv_remove(mrb_state *mrb, mrb_sym sym);
 mrb_value mrb_obj_instance_variables(mrb_state*, mrb_value);
 mrb_value mrb_obj_iv_inspect(mrb_state*, struct RObject*);
 mrb_sym mrb_class_sym(mrb_state *mrb, struct RClass *c, struct RClass *outer);

src/variable.c

@@ -1031,6 +1031,17 @@ mrb_gv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
   iv_put(mrb, t, sym, v);
 }
 
+void
+mrb_gv_remove(mrb_state *mrb, mrb_sym sym)
+{
+  iv_tbl *t;
+
+  if (!mrb->globals) {
+    return;
+  }
+  iv_del(mrb, mrb->globals, sym, NULL);
+}
+
 static int
 gv_i(mrb_state *mrb, mrb_sym sym, mrb_value v, void *p)
 {