bpo-38519: Internal include files missing on Windows (pythonGH-16921)

(cherry picked from commit edb172a)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

Author: miss-islington

Misc/NEWS.d/next/Windows/2019-10-28-05-01-29.bpo-38519.dCkY66.rst

@@ -0,0 +1,2 @@
+Restores the internal C headers that were missing from the nuget.org and
+Microsoft Store packages.

PC/layout/main.py

@@ -216,12 +216,7 @@ def _c(d):
 
     if ns.include_dev:
 
-        def _c(d):
-            if d.is_dir():
-                return d.name != "internal"
-            return True
-
-        for dest, src in rglob(ns.source / "Include", "**/*.h", _c):
+        for dest, src in rglob(ns.source / "Include", "**/*.h"):
             yield "include/{}".format(dest), src
         src = ns.source / "PC" / "pyconfig.h"
         yield "include/pyconfig.h", src