Make maps fields work on installed C++ protobufs.

Change-Id: Id937e25bbb35968ee76c92bd4a8ce6247408c443
diff --git a/Makefile.am b/Makefile.am
index 1c64b71..18b3fe8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -310,10 +310,12 @@
   LICENSE                                                                    \
   CONTRIBUTORS.txt                                                           \
   CHANGES.txt                                                                \
+  config.h.include                                                           \
   editors/README.txt                                                         \
   editors/proto.vim                                                          \
   editors/protobuf-mode.el                                                   \
   vsprojects/config.h                                                        \
+  vsprojects/google/protobuf/stubs/pbconfig.h                                \
   vsprojects/extract_includes.bat                                            \
   vsprojects/libprotobuf.vcproj                                              \
   vsprojects/libprotobuf-lite.vcproj                                         \