fuzz: some improvements and add two new fuzzers (#1881)

Remove `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` define from
`fuzz/Makefile.am`; it is already included by the main configure script
(when fuzzing).

Add a knob to force disabling of AESNI optimizations: this way we can
fuzz also no-aesni crypto code.

Move CRC32 algorithm into the library.

Add some fake traces to extend fuzzing coverage. Note that these traces
are hand-made (via scapy/curl) and must not be used as "proof" that the
dissectors are really able to identify this kind of traffic.

Some small updates to some dissectors:

CSGO: remove a wrong rule (never triggered, BTW). Any UDP packet starting
with "VS01" will be classified as STEAM (see steam.c around line 111).
Googling it, it seems right so.

XBOX: XBOX only analyses UDP flows while HTTP only TCP ones; therefore
that condition is false.

RTP, STUN: removed useless "break"s

Zattoo: `flow->zattoo_stage` is never set to any values greater or equal
to 5, so these checks are never true.

PPStream: `flow->l4.udp.ppstream_stage` is never read. Delete it.

TeamSpeak: we check for `flow->packet_counter == 3` just above, so the
following check `flow->packet_counter >= 3` is always false.

src/lib/protocols/rtp.c

@@ -54,7 +54,6 @@ static u_int8_t isValidMSRTPType(u_int8_t payloadType, enum ndpi_rtp_stream_type
   case 118: /* Comfort Noise Wideband */
     *s_type = rtp_audio;
     return(1 /* RTP */);
-    break;
     
   case 34: /* H.263 [MS-H26XPF] */
   case 121: /* RT Video */
@@ -63,7 +62,6 @@ static u_int8_t isValidMSRTPType(u_int8_t payloadType, enum ndpi_rtp_stream_type
   case 127: /* x-data */
     *s_type = rtp_video;
     return(1 /* RTP */);
-    break;
 
   case 200: /* RTCP PACKET SENDER */
   case 201: /* RTCP PACKET RECEIVER */
@@ -71,7 +69,6 @@ static u_int8_t isValidMSRTPType(u_int8_t payloadType, enum ndpi_rtp_stream_type
   case 203: /* RTCP Bye */
     *s_type = rtp_unknown;
     return(2 /* RTCP */);
-    break;
 
   default:
     return(0);