ubus: update to version 2019-12-19

ubus: update to version 2019-12-19

Contains following changes:

 a1523d76b016 fix blob parsing vulnerability by using blob_parse_untrusted
 c60583743ccf ubus_monitor: workaround possibly false positive uses of memory after it is freed
 dac6c7c575ac ubusd_monitor: fix possible null pointer dereference
 060dfbb26da3 ubus_common: remove duplicate ARRAY_SIZE and add missing include
 c5f2053dfcfd workaround possibly false positive uses of memory after it is freed
 72be8e93f07d lua: ubus_lua_do_subscribe: fix copy&paste error
 a995b1e68129 lua: workaround false positive dereference of null pointer
 08f17c87a000 add fuzzer and cram based unit tests
 c413be9b376c refactor ubusd.c into reusable ubusd_library
 afd47189e864 examples: remove dead increments
 b2e544238672 add initial GitLab CI support
 058f4e9526ed libubus: fix incompatible pointer types assigment
 d2e026a33df8 iron out all extra compiler warnings
 5d7ca8309d0a ubusd/libubus-io: fix variable sized struct position warning
 d61282db5640 ubusd: fix comparison of integers of different signs
 90fb16234c22 cmake: enable extra compiler checks

and bumps ABI_VERSION to 20191219.

Signed-off-by: Petr Štetiar <ynezz@true.cz>