Makefile: Remove warning (-Wdeclaration-after-statement)
          This construct, known from C++, was introduced with ISO C99 and is
          by default allowed in GCC. It is not supported by ISO C90 and
          was not supported by GCC versions before GCC 3.0.

          As we use GCC >4.3.3, this isn't needed anymore.

Change-Id: Ia9d593ab6aaedd02b56c098a191e96052afad189