Rename hb-*private.hh to hb-*.hh

Sorry for the noise, downstream custom builders.  Please adjust.
diff --git a/src/hb-ot-shape-complex-use-machine.hh b/src/hb-ot-shape-complex-use-machine.hh
index 0ec805a..77ca3ae 100644
--- a/src/hb-ot-shape-complex-use-machine.hh
+++ b/src/hb-ot-shape-complex-use-machine.hh
@@ -31,7 +31,7 @@
 #ifndef HB_OT_SHAPE_COMPLEX_USE_MACHINE_HH
 #define HB_OT_SHAPE_COMPLEX_USE_MACHINE_HH
 
-#include "hb-private.hh"
+#include "hb.hh"
 
 
 #line 38 "hb-ot-shape-complex-use-machine.hh"