protoc-c/main.cc: add a version string to protoc-c based on the

PACKAGE_STRING provided by autotools (fixes #52)

protoc-c/main.cc

@@ -10,5 +10,8 @@ int main(int argc, char* argv[]) {
   cli.RegisterGenerator("--c_out", &c_generator,
   "Generate C/H files.");
 
+  // Add version info generated by automake
+  cli.SetVersionInfo(PACKAGE_STRING);
+  
   return cli.Run(argc, argv);
 }