Remove some easy obj.h dependencies.

A lot of consumers of obj.h only want the NID values. Others didn't need
it at all. This also removes some OBJ_nid2sn and OBJ_nid2ln calls in EVP
error paths which isn't worth pulling a large table in for.

BUG=chromium:499653

Change-Id: Id6dff578f993012e35b740a13b8e4f9c2edc0744
Reviewed-on: https://boringssl-review.googlesource.com/7563
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/d1_lib.c b/ssl/d1_lib.c
index 76498cc..4298580 100644
--- a/ssl/d1_lib.c
+++ b/ssl/d1_lib.c
@@ -61,7 +61,7 @@
 
 #include <openssl/err.h>
 #include <openssl/mem.h>
-#include <openssl/obj.h>
+#include <openssl/nid.h>
 
 #include "internal.h"