Test linking against camlp4 (fix Homebrew#39399)

And bump revision to force bottles being rebuilt for ocaml 4.07.1.

Formula/camlp4.rb

@@ -4,6 +4,7 @@ class Camlp4 < Formula
   url "https://github.com/ocaml/camlp4/archive/4.07+1.tar.gz"
   version "4.07+1"
   sha256 "ecdb8963063f41b387412317685f79823a26b3f53744f0472058991876877090"
+  revision 1
   head "https://github.com/ocaml/camlp4.git", :branch => "trunk"
 
   bottle do
@@ -35,5 +36,8 @@ def install
                             "foo.ml", "-o", testpath/"foo.ml.out"
     assert_equal "type t = [ Homebrew | Rocks ];",
                  (testpath/"foo.ml.out").read.strip
+
+    (testpath/"try_camlp4.ml").write "open Camlp4"
+    system "ocamlc", "-c", "-I", "/usr/local/lib/ocaml/camlp4", "-o", testpath/"try_camlp4.cmo", testpath/"try_camlp4.ml"
   end
 end