configure: add endian check

Will remove guesswork and manual hacking in the OS headers.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/server.c b/server.c
index ffa6ed4..bb03c77 100644
--- a/server.c
+++ b/server.c
@@ -403,7 +403,7 @@
 
 	memset(&probe, 0, sizeof(probe));
 	gethostname((char *) probe.hostname, sizeof(probe.hostname));
-#ifdef FIO_BIG_ENDIAN
+#ifdef CONFIG_BIG_ENDIAN
 	probe.bigendian = 1;
 #endif
 	strncpy((char *) probe.fio_version, fio_version_string, sizeof(probe.fio_version));