Add type checking to 16/32/64 endianness converters

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/stat.h b/stat.h
index 507a76a..cba8714 100644
--- a/stat.h
+++ b/stat.h
@@ -115,8 +115,8 @@
 struct thread_stat {
 	char name[FIO_JOBNAME_SIZE];
 	char verror[FIO_VERROR_SIZE];
-	int32_t error;
-	int32_t groupid;
+	uint32_t error;
+	uint32_t groupid;
 	uint32_t pid;
 	char description[FIO_JOBNAME_SIZE];
 	uint32_t members;
@@ -163,7 +163,7 @@
 	 */
 	uint16_t continue_on_error;
 	uint64_t total_err_count;
-	int32_t first_error;
+	uint32_t first_error;
 
 	uint32_t kb_base;
 };