Fix compiler warning: 'implicit-function-declaration'

Changes fix follwoing warnings:
- tests/adaptation/security/ndn-lite-rng-posix-crypto-impl.c:31:18: error: implicit declaration of function ‘read’; did you mean ‘creat’?

Author: yan-foto

tests/adaptation/security/ndn-lite-rng-posix-crypto-impl.c

@@ -12,6 +12,7 @@
 #include <ndn-lite/security/ndn-lite-rng.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <unistd.h>
 #if defined(__APPLE__)
   #include <stdlib.h>
 #endif