Closes #1519. Thanks to Christoph Krey.

Default behaviour for v5 clients using `-c` is now to use infinite length
sessions, as with v3 clients.

Closes #1546. Thanks to Kiran Pradeep.

Signed-off-by: Gianfranco Costamagna <costamagnagianfranco@yahoo.it>

Bugfix: enabling DLT was overriding everything else on linker flags because of error in cmake set keyword

Signed-off-by: Gianfranco Costamagna <costamagnagianfranco@yahoo.it>

Signed-off-by: Gianfranco Costamagna <costamagnagianfranco@yahoo.it>

This means `--remove-retained -t bbc/# -T bbc/one/#` would remove all
retained messages in `bbc/#`, instead of leaving all of the topics in
`bbc/one/#`.

Closes #1585. Thanks to Simon Moser.

Covers when loading certificates fails, or there are ENGINE problems.

Closes #1552. Thanks to Michael Richardson.

Closes #1584. Thanks to panava.

Closes #1533. Thanks to Markus Gothe.

Closes #1539. Thanks to CliveJL and LeonPoon.

Closes #1523. Thanks to Basavesh Shivakumar.

Merge branch 'bugfix-MemLeak_in_handle_unsubscribe' of git://github.com/panava/mosquitto into panava-bugfix-MemLeak_in_handle_unsubscribe

Merge branch 'bugfix-NullDeref_in_util_mosc.c' of git://github.com/panava/mosquitto into panava-bugfix-NullDeref_in_util_mosc.c

Merge branch 'bugfix-MemoryLeak_in_persist_read' of git://github.com/panava/mosquitto into panava-bugfix-MemoryLeak_in_persist_read

Closes #1548.

Reason: In lines 435 and 439, the function returns without calling closing
fptr which was opened at line 399.

Fix: I added fclose(fptr) statements before each of the returns.
Signed-off-by: Panagiotis Vasilikos <panagiotis.vasilikos@alexandra.dk>

Reason: There is no check that the mosquitto__malloc at line 162 was sucessfull.
This could result to a Null pointer dereference in the memcpy call at line 166.

Fix: I added the check.
Signed-off-by: Panagiotis Vasilikos <panagiotis.vasilikos@alexandra.dk>

Closes #1550. Thanks to Markus Gothe.

Closes #1564. Thanks to back1127.

This is when due to not being able to open a listening socket, solved by
calling freeaddrinfo in the error cases.

Closes #1565. Thanks to back1127.

Closes #1566. Thanks to kollokollo.

Reason: In line 70, the memory allocation for the pointer reasons_codes may
result to a memory leak due to the many returns (e.g as the one in line 78)
occuring in the program's path until reaching the mosquitto__free at line 122.

Fix: I added a mosquitto__free(reason_codes) statement before each return
statement that could result to a memory leak

Signed-off-by: Panagiotis Vasilikos <panagiotis.vasilikos@alexandra.dk>

Reason: The memory allocated for the packet pointer at line 155 is not freed
before returning at line 188.

Fix: I inserted the mosquitto__free(packet) statement just before returning
at line 188.

Signed-off-by: Panagiotis Vasilikos <panagiotis.vasilikos@alexandra.dk>

Reason: In line 70, the memory allocation for the pointer reasons_codes may
result to a memory leak due to the many returns (e.g as the one in line 78)
occuring in the program's path until reaching the mosquitto__free at line 122.

Fix: I moved the memory allocation code block (lines 69-73) just before
the line 102. This is the first place the pointer reason_codes is used, while
the following mosquitto__free operators free the allocated memory correctly.

Signed-off-by: Panagiotis Vasilikos <panagiotis.vasilikos@alexandra.dk>

Coverity Scan 1405815.

Coverity Scan 1400727.

Previously, authentication checks would only take place if usernames
were defined in the password file.

Closes #1545. Thanks to Timothy Godfrey.

Closes #1539. Thanks to Leon Poon.