Fix Bug #10348 Different dissection results for same file.
The fault is that reassembly_table_init() must be called when reloading
the file - move it to an init routine and register the init routine.
While there move the proto_register_opcua() routine to the end of the file
to be more consistent with other dissectors.
Change soft deprecated APIs

Change-Id: I2b93692be24dbf60f4ef09aa7283e55ebf3c1874
Reviewed-on: https://code.wireshark.org/review/3431
Reviewed-by: Anders Broman <a.broman58@gmail.com>
(cherry picked from commit 79c55a34cb9869a846ed4e58a760c50e409eeeb5)
Reviewed-on: https://code.wireshark.org/review/3468