build: Experimental support to build using precompiled headers

This type of build needs to be explicitly enabled using --with-pch
configure option.

Change-Id: I02dc304187d54c3cf40f1d51b1b11b21f868e225
diff --git a/src/data.cpp b/src/data.cpp
index 85d87a5..00a915c 100644
--- a/src/data.cpp
+++ b/src/data.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "common.hpp"
+
 #include "data.hpp"
 
 using namespace std;