use full prototypes

src/cmd/sam/disk.c

diff --git a/src/cmd/sam/disk.c b/src/cmd/sam/disk.c
index f27e94b..81c9838 100644
--- a/src/cmd/sam/disk.c
+++ b/src/cmd/sam/disk.c
@@ -25,7 +25,7 @@
 #endif
 
 Disk*
-diskinit()
+diskinit(void)
 {
 	Disk *d;