deps: fix missing include of <algorithm> in bignum.cc

This should include <algorithm> for std::min, otherwise it would not
build with newer libstdc++.

Author: joyeecheung

common.gypi

@@ -44,7 +44,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.6',
+    'v8_embedder_string': '-node.7',
 
     ##### V8 defaults for Node.js #####