FStream: Include Configure.hxx before other headers

In commit 15e90a3c (Sort includes to stabilize include order w.r.t.
clang-format, 2016-11-04) we forgot to move `Configure.hxx` into its own
block to ensure it remains first.  Restore the original include order
and add separating blanks to make it stable w.r.t. clang-format.

Change-Id: Ibca524065147192da916ad98d7db3c5d86b26a5a

FStream.hxx.in

@@ -3,9 +3,11 @@
 #ifndef @KWSYS_NAMESPACE@_FStream_hxx
 #define @KWSYS_NAMESPACE@_FStream_hxx
 
-#include <fstream>
 #include <@KWSYS_NAMESPACE@/Configure.hxx>
+
 #include <@KWSYS_NAMESPACE@/Encoding.hxx>
+
+#include <fstream>
 #if defined(_WIN32)
 #if !defined(_MSC_VER) && @KWSYS_NAMESPACE@_CXX_HAS_EXT_STDIO_FILEBUF_H
 #include <ext/stdio_filebuf.h>