sl: allow send_reply() in the route block types supported by t_reply() and sl_send_reply()

- reported by Juha Heinanen, FS#362

(cherry picked from commit c77aaf38eafe1d3549d266feebf76ac0b50738ea)
sl: docs updated to reflect usage of send_reply()

(cherry picked from commit e7b73f7e0160eac1ca445201fbf796df0dd13ce0)
sl: README updated
modules/registrar: Invalidate temporary GRUUs when the Call-ID changes for a sip.instance
- Fixes FS#368
(cherry picked from commit 27eba09b603b265ce4213d238c132249189ae6e8)
modules/usrloc: Update contact field when updating a contact in the DB
- Fixes FS#368
(cherry picked from commit a55018deb431ef32ee2bcd45610903327850757d)
modules/avpops: Fix 'uninitialised variable' warning
(cherry picked from commit 54020b00893ee259baee714d7d17adc6d31f9112)
rtpproxy-ng: remove trailing double \r\n from multipart SDP
modules/ndb_redis: solved bug in second call to redisvCommand.

(cherry picked from commit 52a34d269931f6f3a50b3fc532405624b9e38d23)
modules/ims_registrar_pcscf: fix log
permissions: re-init db connection for reload cmd

- some workers for specific mi/rpc commands may not have a db connection from the start

(cherry picked from commit cb23be9456c178957399ec9d8ce8a1420d50fc32)
tls: clarified licensing based on development history

- some were c&p as they refered to files related to components that were
  developed later than the (c) year (e.g., selects)
- added openssl exception to gpl parts based on agreement from the
  developers of those components - most of the code was released long time
  ago under BSD by iptelorg. Code was rewrote for 3.1 when asynchronous
  support was developed.

(cherry picked from commit 7771e9cdb58ea1cef008e2a70f53c5f183c26ebe)
tm: propagate reply/failure route indexes to local uac branch

- affects the updates done in event_route[tm:local-request]
- reported by Pawel Sternal, FS#371

(cherry picked from commit 715ba52de2031786fd9f05832d5bf73d17d46e47)
tm: exported set_t() and get_t_branch() viam tm api

- allows to backup and restore pointers to T and branch

(cherry picked from commit 777dd5e28ff6b4fcc3b1c44e841eb415c974075f)
tmx: backup and restore existing T and branch pointers for t_cancel_callid()

- reported and initial patch by Guillaume Bour

(cherry picked from commit 60372d613544af1f8f06122eb77fa2a9636a6c3a)
Makefile.defs: version set to 4.1.0-rc2
mem: malloc(0) should return a valid pointer for free according to specs

(cherry picked from commit f61ff34aac7c7bae3a96fb698a899c8a0e692a9f)
kamailio.cfg: use set_contact_alias() instead of add_contact_alias()

(cherry picked from commit 66ed11c90e38d948fd75f908b3edd409bca74134)
kamailio.cfg: updated the comment about kamailio version
pkg/kamailio/centos: Updated rel in .spec in preparation for 4.1.0 release
stun: updated docs to reflect that it no longer depends on external libs

(cherry picked from commit 305e7b5693e71d2027f8e6462129f8c9f01ad76d)