Fix headers.

src/common/buffer.cpp

@@ -18,7 +18,7 @@
 
 #include "buffer.h"
 
-#include "common.h"
+#include <stdexcept>
 
 #include <stdio.h>
 

src/db_add_language/db_add_language.cpp

@@ -32,9 +32,10 @@
 #include <fstream>
 #include <iostream>
 #include <iomanip>
-#include <math.h>
 #include <numeric>
 
+#include <math.h>
+
 // MultiByteToWideChar: https://msdn.microsoft.com/en-us/library/windows/desktop/dd319072(v=vs.85).aspx
 // code pages: https://msdn.microsoft.com/en-us/library/windows/desktop/dd317756(v=vs.85).aspx
 const std::map<std::string, int> code_pages