http: move OutgoingMessage into it's own file
diff --git a/node.gyp b/node.gyp
index 36c05cf..210dcd8 100644
--- a/node.gyp
+++ b/node.gyp
@@ -37,6 +37,7 @@
       'lib/_http_agent.js',
       'lib/_http_common.js',
       'lib/_http_incoming.js',
+      'lib/_http_outgoing.js',
       'lib/https.js',
       'lib/module.js',
       'lib/net.js',