Add missing include statement for ssize_t

Compilation of code which uses libtiff fails when ssize_t is undefined:

openjpeg/thirdparty/libtiff/tif_config.h:324:22:
 error: unknown type name ‘ssize_t’
 #define TIFF_SSIZE_T ssize_t
                      ^
openjpeg/thirdparty/libtiff/tiffio.h:67:9: note:
 in expansion of macro ‘TIFF_SSIZE_T’
 typedef TIFF_SSIZE_T tmsize_t;
         ^

Add the missing include statement.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

src/bin/jp2/converttif.c

@@ -42,6 +42,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <unistd.h>
 
 #ifndef OPJ_HAVE_LIBTIFF
 # error OPJ_HAVE_LIBTIFF_NOT_DEFINED

tests/compare_images.c

@@ -37,6 +37,7 @@
 #include <string.h>
 #include <ctype.h>
 #include <assert.h>
+#include <unistd.h>
 
 #include "opj_apps_config.h"
 #include "opj_getopt.h"