Make strcmp in main.c#_start_logging explicit

Currently the don't pipe to standard output options are in the else branch, because of usage of strcmp such as if ( strcmp(a, b) ) { .

This gist https://gist.github.com/miksago/cfb3f41784bff197facc includes changes to make the comparison of strings explicit as well as changes the logic to be:

if config->access_log == '-'; then
    handle standard output
else
    handle logging