add compat/tap

To keep backward compatibility for API name changing.

Library/Homebrew/compat.rb

@@ -1,4 +1,5 @@
 require "compat/fails_with_llvm"
+require "compat/tap"
 require "compat/formula"
 require "compat/formula_specialties"
 require "compat/hardware"

Library/Homebrew/compat/tap.rb

@@ -0,0 +1,9 @@
+require "tap"
+
+class Tap
+  def core_formula_repository?
+    core_tap?
+  end
+end
+
+CoreFormulaRepository = CoreTap