silence a couple of compiler warnings about pointer signedness

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@7430 65c4cc65-6c06-0410-ace0-fbb531ad65f3

utils/astman.c

@@ -660,8 +660,8 @@ static int login(char *hostname)
 				struct MD5Context md5;
 				unsigned char digest[16];
 				MD5Init(&md5);
-				MD5Update(&md5, challenge, strlen(challenge));
-				MD5Update(&md5, pass, strlen(pass));
+				MD5Update(&md5, (unsigned char *)challenge, strlen(challenge));
+				MD5Update(&md5, (unsigned char *)pass, strlen(pass));
 				MD5Final(digest, &md5);
 				for (x=0; x<16; x++)
 					len += sprintf(md5key + len, "%2.2x", digest[x]);