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

This resulted in the main loop being indefinitely stuck into write() into a file descriptor.

Fix invalid read after DNS TTL expiration in channel.c It resulted in the connection being restarted.

(cherry picked from commit a96d9585)

Fixes resolver_results not providing srv results, and remove trailing '.' at the end of SRV targets.

Fix several invalid reads in tester, and potential crash and use of unitialized value in http proxy support.

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.

Refused uri with "@" but no username

fix(dialog): use type belle_sip_header_require_t instead common type of headers in function belle_sip_dialog_process_response_100rel

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