Update libsrtp to 1.5.2

srtp/test/rtpw.c

Index: srtp/test/rtpw.c
diff --git a/srtp/test/rtpw.c b/srtp/test/rtpw.c
index 17f27f278136bfb72c451b182878f75a6f8c9421..9d560b6d069f461d0d46a1538c196c3fe6086775 100644
--- a/srtp/test/rtpw.c
+++ b/srtp/test/rtpw.c
@@ -68,6 +68,9 @@
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>         /* for close()         */
+#elif defined(_MSC_VER)
+#include <io.h>             /* for _close()        */
+#define close _close
 #endif
 #ifdef HAVE_SYS_SOCKET_H
 # include <sys/socket.h>
@@ -470,7 +473,7 @@ main (int argc, char *argv[]) {
 	      expected_len, len);
       exit(1);    
     } 
-    if (strlen(input_key) > policy.rtp.cipher_key_len*2) {
+    if ((int) strlen(input_key) > policy.rtp.cipher_key_len*2) {
       fprintf(stderr, 
 	      "error: too many digits in key/salt "
 	      "(should be %d hexadecimal digits, found %u)\n",