use picrin's strdup impl if possible

src/blob.c

@@ -30,7 +30,7 @@ pic_blob_new(pic_state *pic, char *dat, size_t len)
   struct pic_blob *bv;
 
   bv = (struct pic_blob *)pic_obj_alloc(pic, sizeof(struct pic_blob), PIC_TT_BLOB);
-  bv->data = strndup(dat, len);
+  bv->data = pic_strndup(pic, dat, len);
   bv->len = len;
   return bv;
 }

src/error.c

@@ -131,7 +131,7 @@ pic_error_error(pic_state *pic)
 
   e = (struct pic_error *)pic_obj_alloc(pic, sizeof(struct pic_error), PIC_TT_ERROR);
   e->type = PIC_ERROR_OTHER;
-  e->msg = strdup(str);
+  e->msg = pic_strdup(pic, str);
   e->irrs = pic_list_from_array(pic, argc, argv);
 
   pic_raise(pic, pic_obj_value(e));

src/string.c

@@ -13,7 +13,7 @@ pic_str_new(pic_state *pic, const char *cstr, size_t len)
 
   str = (struct pic_string *)pic_obj_alloc(pic, sizeof(struct pic_string), PIC_TT_STRING);
   str->len = len;
-  str->str = strdup(cstr);
+  str->str = pic_strdup(pic, cstr);
   return str;
 }
 

src/symbol.c

@@ -31,7 +31,7 @@ pic_intern_cstr(pic_state *pic, const char *str)
     pic->sym_pool = pic_realloc(pic, pic->sym_pool, sizeof(const char *) * pic->scapa);
   }
   id = pic->slen++;
-  pic->sym_pool[id] = strdup(str);
+  pic->sym_pool[id] = pic_strdup(pic, str);
   xh_put(pic->sym_tbl, str, id);
   return id;
 }