A scope is a section name between square bracket, alone on its line, ie:
[scope-name]
...
The spaces at the beginning and at the end of the line are skipped. Comments at
the end of the line are also skipped.
When a scope is parsed, its name is saved in the global variable
cfg_scope. Initially, cfg_scope is NULL and it remains NULL until a valid scope
line is parsed.
This feature remains unused in the HAProxy configuration file and
undocumented. However, it will be used during SPOE configuration parsing.