Examples/*coder.c: add missing include of unistd.h

Fix warning: implicit declaration of function 'getcwd' is invalid in
C99 [-Wimplicit-function-declaration]

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>

Examples/decoder.c

@@ -62,6 +62,7 @@ same arguments, and encoder.c does error check.
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <unistd.h>
 #include <sys/time.h>
 #include <sys/stat.h>
 #include <signal.h>

Examples/encoder.c

@@ -59,6 +59,7 @@ is the file name with "_k#" or "_m#" and then the extension.
 #include <time.h>
 #include <sys/time.h>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>