Fixed memory leak in 'OTF_vsnprintf()'

This commit was SVN r19842.

ompi/contrib/vt/vt/extlib/otf/otflib/OTF_Platform.c

@@ -243,6 +243,9 @@ int OTF_vsnprintf(char* str, size_t size, const char* fmt, va_list ap) {
 		}
 	}
 
+	/* free allocated buffer */
+	free(buf);
+
 	return length;
 }