Support ; as comment character in config file

[uniwangshan@…]

Currently # is hardcoded as comment character, but for ini file, both # and ; are widely used as comment characters.

Because program_options doesn't allow a non-section line without =, the config file parsing will fail if there are ; comments which doesn't have = in it.

For example, this line will fail to parse:

; This is a comment

The easiest fix will be adding check of ; in common_config_file_iterator::get()

Thanks.