Added syslogd functionality

[Cvetomird91]

Hello,

I noticed that the pCloud console client didn't log messages to the Linux logging facility. I used syslog.h to add this functionality. I tested it on Fedora 25, which directly logs the messages to the systemd logging facility.

[sergeyklay]

How about this :)

https://github.com/pcloudcom/console-client/blob/2ecb7c981554499501f0a4f0512bd7a1a483645b/pCloudCC/lib/pclsync/plibs.h#L58-L60

As well as:

$ grep -E -nr 'tmp.*\.log' ./pCloudCC 2>/dev/null
./pCloudCC/lib/poverlay_linux/debug.h:25:#define DEBUG_FILE "/tmp/overlay_client.log"
./pCloudCC/lib/pclsync/plibs.h:59:#define DEBUG_FILE "/tmp/psync_err.log"
./pCloudCC/lib/pclsync/lib/poverlay/ShellExt.cpp:34:  _logfile.open("c:\\tmp\\overlaydll.log", std::fstream::out | std::fstream::app | std::fstream::ate);
./pCloudCC/lib/pclsync/lib/poverlay_linux/debug.h:25:#define DEBUG_FILE "/tmp/overlay_client.log"

[Cvetomird91]

@sergeyklay thanks for addressing this PR. :) Do you suggest using those macros instead of logging to syslog?

[sergeyklay]

@Cvetomird91 I mean, this PR don't completely cover the idea of logging and actually just add +1 place where the logs might be. It would be better to either get rid of the files altogether, or write only to files (in terms of consistency and program design).