Vendor GYP and libuv into the repo.

Instead of dynamically downloading these as needed during a build, this
checks in those two dependencies directly into the Wren repo. That's a
little lame because users of Wren who aren't building the CLI don't
actually need them, but they aren't too big, so it's not a huge deal.

It makes builds (particularly on Travis) more reliable, because they
don't have to pull down additional content over the network.

deps/libuv/libuv.pc.in

@@ -0,0 +1,11 @@
+prefix=@prefix@
+exec_prefix=${prefix}
+libdir=@libdir@
+includedir=@includedir@
+
+Name: @PACKAGE_NAME@
+Version: @PACKAGE_VERSION@
+Description: multi-platform support library with a focus on asynchronous I/O.
+
+Libs: -L${libdir} -luv @LIBS@
+Cflags: -I${includedir}