Fix a few casting warnings.

Signed-off-by: Patrick Hogan <pbhogan@gmail.com>

src/etc.c

@@ -31,7 +31,7 @@ mrb_data_object_alloc(mrb_state *mrb, struct RClass *klass, void *ptr, const str
 
   data = mrb_obj_alloc(mrb, MRB_TT_DATA, klass);
   data->data = ptr;
-  data->type = type;
+  data->type = (struct mrb_data_type *) type;
 
   return data;
 }

src/parse.y

@@ -4658,7 +4658,7 @@ parser_new(mrb_state *mrb)
   p->cmd_start = TRUE;
   p->in_def = p->in_single = FALSE;
 
-  p->capture_errors = NULL;
+  p->capture_errors = 0;
 
   p->lineno = 1;
 #if defined(PARSER_TEST) || defined(PARSER_DEBUG)

src/proc.c

@@ -30,7 +30,7 @@ mrb_closure_new(mrb_state *mrb, mrb_irep *irep)
   struct REnv *e;
 
   if (!mrb->ci->env) {
-    e = mrb_obj_alloc(mrb, MRB_TT_ENV, mrb->ci->proc->env);
+    e = mrb_obj_alloc(mrb, MRB_TT_ENV, (struct RClass *) mrb->ci->proc->env);
     e->flags= (unsigned int)irep->nlocals;
     e->mid = mrb->ci->mid;
     e->cioff = mrb->ci - mrb->cibase;