src: add include guards to internal headers

For consistency with the newly added src/base64.h header, check that
NODE_WANT_INTERNALS is defined and set in internal headers.

PR-URL: https://github.com/nodejs/node/pull/6948
Refs: https://github.com/nodejs/node/pull/6910
Reviewed-By: Fedor Indutny <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Trevor Norris <[email protected]>
diff --git a/node.gyp b/node.gyp
index 86dffef..0d32905 100644
--- a/node.gyp
+++ b/node.gyp
@@ -706,6 +706,7 @@
         'GTEST_DONT_DEFINE_ASSERT_LE=1',
         'GTEST_DONT_DEFINE_ASSERT_LT=1',
         'GTEST_DONT_DEFINE_ASSERT_NE=1',
+        'NODE_WANT_INTERNALS=1',
       ],
       'sources': [
         'test/cctest/util.cc',