Increase OPT_LEN_MAX

When I run fio with lots of files on a disk, parameter filename's length
is more than 1024 and tail filenames are cut.

Below is a patch to increase OPT_LEN_MAX to 4096.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/parse.h b/parse.h
index 5b1a53d..ae6bdea 100644
--- a/parse.h
+++ b/parse.h
@@ -25,7 +25,7 @@
 	const char *help;		/* help text for sub option */
 };
 
-#define OPT_LEN_MAX 	1024
+#define OPT_LEN_MAX 	4096
 #define PARSE_MAX_VP	16
 
 /*