Merge pull request #1578 from wal-rus/cmake-install-namespace

Add protobuf:: namespace to installed targets
diff --git a/cmake/install.cmake b/cmake/install.cmake
index e096265..4d09955 100644
--- a/cmake/install.cmake
+++ b/cmake/install.cmake
@@ -92,6 +92,7 @@
 
 install(EXPORT protobuf-targets
   DESTINATION "${CMAKE_INSTALL_CMAKEDIR}"
+  NAMESPACE protobuf::
   COMPONENT protobuf-export)
 
 configure_file(protobuf-config.cmake.in