This option makes the creation of 'package_source' custom target optional,
allowing to build with CMake < 3.11 if it is disabled (default).

(cherry picked from commit 4d01e33b)

Fix build error due to API change of bctbx_create_file_log_handler()

See merge request !5

added chmod to give exec rights on shared libs for ubuntu packaging

See merge request !4

Fix compilation errors

See merge request !3

Tests: changes following factorization of logs options into bc_tester

See merge request !1

Fix/rpm install libdir

See merge request !2

Add a mutex on database access
API with direct cache access is deprecated

+fix memory leaks in tests

gcc was right to complain!

+ improve code readability

Retrocompatibility ensured by build option which is on by default for now.

- this function shall be used in a mono-device per account environment
- give the trust status of a peer uri based on the
last device involved in a ZRTP exchange associated to that uri.

+ do not store in cache any peer information until first negotiation succeeds

- better trace
- fix bug in ECDH specifics tests

Do not append project build version to package name if it is 0 (that's the case for tagged releases).