Restore belle_sip_random(). No reason to change the public API. This function is used by presence server.

+ belle_sip_random is used only internally and be more precise on its return type

Allow the channel to know which hostname it is connected to in case of SRV resolution. THis will avoid a DNS resolution when resolving record-routes in dialogs.
This change required a refactoring of resolver code. A new object belle_sip_resolver_results_t is introduced to provide addrinfos together with dns srv records.

final 100rel commit. belle_sip_dialog_tester work with test 'Simple call with prack' for testing PRACK message.

fix(belle-sip): disable new gcc 8 -Wcast-function-type warnings (FIXME in the future) + use correct copyright headers... (Not a mixed tab/spaces format!)

Add two callbacks in belle_tls_crypto_config_t for TLS handshake control: for individual certificate check, and for a postcheck of the peer certificate.

fix(BodyHandler): belle_sip_multipart_body_handler_new_from_buffer use now a const void* parameter instead of void* (buffer is not modified after all)

The are going to be used to implement a kind of floating ref for liblinphone C objects.

extend the notion of automatic contact to header_address, so that refer-to can be benefit from this option as well.