bindings/cxx: include config.h as early as possible

Move the inclusion of <config.h> before any other source code.

bindings/cxx/ConfigKey_methods.cpp

@@ -1,3 +1,5 @@
+#include <config.h>
+
 const DataType *ConfigKey::data_type() const
 {
 	const struct sr_key_info *info = sr_key_info_get(SR_KEY_CONFIG, id());
@@ -30,8 +32,6 @@ const ConfigKey *ConfigKey::get_by_identifier(string identifier)
 	return get(info->key);
 }
 
-#include <config.h>
-
 #ifndef HAVE_STOI_STOD
 
 /* Fallback implementation of stoi and stod */