Eclipse Mosquitto™ 2.0.7

Broker:

- Fix exporting of executable symbols on BSD when building via makefile.

- Fix some minor memory leaks on exit only.

- Fix possible memory leak on connect. Closes #2057.

- Fix openssl engine not being able to load private key. Closes #2066.

Clients:

- Fix config files truncating options after the first space. Closes #2059.

Build:

- Fix man page building to not absolutely require xsltproc when using CMake.

  This now handles the case where we are building from the released tar, or

  building from git if xsltproc is available, or building from git if xsltproc

  is not available.