Fix implicit declaration of functions.
--- src/pathexec_run.c.orig
+++ src/pathexec_run.c
@@ -1,5 +1,6 @@
 /* Public domain. */
 
+#include <unistd.h>
 #include "error.h"
 #include "stralloc.h"
 #include "str.h"
--- src/prot.c.orig
+++ src/prot.c
@@ -1,5 +1,6 @@
 /* Public domain. */
 
+#include <unistd.h>
 #include "hasshsgr.h"
 #include "prot.h"
 
--- src/seek_set.c.orig
+++ src/seek_set.c
@@ -1,6 +1,7 @@
 /* Public domain. */
 
 #include <sys/types.h>
+#include <unistd.h>
 #include "seek.h"
 
 #define SET 0 /* sigh */