[rtmpdump] [PATCH] fix build with polarssl-1.3.x

[hasufell]

I did not do much testing here, since I don't use rtmpdump.

Also see
https://polarssl.org/kb/how-to/migrate-from-polarssl-1.2-to-polarssl-1.3
for reference which also explains why ssl_set_ciphersuites() has been
removed completely.