Bug 1374699 - fixing compiler warnings for nICEr. r=drno

Cleaning up compiler warnings for nICEr.  Major highlights:
 - set _WINSOCK_DEPRECATED_NO_WARNINGS define in nicer.gyp for Windows
   builds of nICEr to avoid warnings about inet_addr use in ice_ctx.c:102,
   ice_ctx.c:297, ice_parser.c:465, and transport_addr_reg.c:143.
 - move nr_ice_accumulate_count from ice_ctx.{h|c} to stun_util.{h|c}
   as nr_accumulate_count to quiet warnings in turn_client_ctx.c and
   stun_client_ctx.c.
 - stun_msg.{h|c} - change nr_stun_attr_data_.length,
   nr_stun_message_attribute.encoding_length and nr_stun_message_.length
   from int to UINT2 (not size_t since other lengths in this header are
   UINT2).
 - stun_codec.{h|c} - lengths and offsets changed from int to UINT2 to
   match changes in stun_msg.{h|c}
 - r_data.{h|c} - change Data.len from int to size_t
 - nr_crypto.{h|c} - change nr_ice_crypto_vtbl_ lengths from int to size_t

MozReview-Commit-ID: EF5v79RpqbI