libctf: add some missing #includes.

Causes warnings on (at least) recent FreeBSD.

libctf/
	* ctf-create.c: Include <unistd.h>.
	* ctf-open-bfd.c: Likewise.

libctf/ChangeLog

@@ -1,3 +1,8 @@
+2020-06-26  Nick Alcock  <nick.alcock@oracle.com>
+
+	* ctf-create.c: Include <unistd.h>.
+	* ctf-open-bfd.c: Likewise.
+
 2020-06-26  Nick Alcock  <nick.alcock@oracle.com>
 
 	PR libctf/25120

libctf/ctf-create.c

@@ -21,6 +21,7 @@
 #include <sys/param.h>
 #include <assert.h>
 #include <string.h>
+#include <unistd.h>
 #include <zlib.h>
 
 #ifndef roundup

libctf/ctf-open-bfd.c

@@ -25,6 +25,7 @@
 #include <errno.h>
 #include <string.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <elf.h>
 #include <bfd.h>
 #include "swap.h"