CMake: Install .pc Files

Adds pkg-config (`.pc`) files for CMake based installs.
diff --git a/cmake/protobuf-lite.pc.cmake b/cmake/protobuf-lite.pc.cmake
new file mode 100644
index 0000000..cbe5426
--- /dev/null
+++ b/cmake/protobuf-lite.pc.cmake
@@ -0,0 +1,11 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=@CMAKE_INSTALL_PREFIX@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: Protocol Buffers
+Description: Google's Data Interchange Format
+Version: @protobuf_VERSION@
+Libs: -L${libdir} -lprotobuf-lite @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @CMAKE_THREAD_LIBS_INIT@
+Conflicts: protobuf