mpi: Suppress newer gcc warnings.

[Dmitry Eremin-Solenikov]

Hello,

I see a typo in a definition of GCC_ATTR_UNUSED macro:

+#if __GNUC__ > 2 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 5 )
+#define GCC_ATTR_UNUSED  __attribute__ ((unused))
+#else

First line will be true for all gcc starting gcc 3.0, not 3.5.
The comparison line should read

+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 5 )

Shall it not?

-- 
With best wishes
Dmitry