Update libsrtp to 1.5.2

srtp/crypto/math/datatypes.c

 /*
  * datatypes.c
  *
  * data types for finite fields and functions for input, output, and
  * manipulation
  *
  * David A. McGrew
  * Cisco Systems, Inc.
  */
 /*
@@ skipping 517 matching lines @@
   } while (++s < end);
   
 }
 
 #ifdef TESTAPP_SOURCE
 
 static const char b64chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
   "abcdefghijklmnopqrstuvwxyz0123456789+/";
 
 static int base64_block_to_octet_triple(char *out, char *in) {
-  unsigned char sextets[4] = {};
+  unsigned char sextets[4] = {0};
   int j = 0;
   int i;
 
   for (i = 0; i < 4; i++) {
     char *p = strchr(b64chars, in[i]);
     if (p != NULL) sextets[i] = p - b64chars;
     else j++;
   }
 
   out[0] = (sextets[0]<<2)|(sextets[1]>>4);
@@ skipping 11 matching lines @@
   while (i < len && j == 0) {
     j = base64_block_to_octet_triple(out + k, in + i);
     k += 3;
     i += 4;
   }
   *pad = j;
   return i;
 }
 
 #endif