[PATCH]: Check for duplicated conflicting proxies

Hello,

Currently haproxy accepts a config with duplicated proxies (listen/fronted/backed/ruleset). This patch fix this, so the application will complain when there is an error.

With this modification it is still possible to use the same name for two proxies (for example frontend&backend) as long there is no conflict:

 		listen backend frontend ruleset
listen             -      -       -        OK
backend            -      -       OK       OK
frontend           -      OK      -        OK
ruleset            OK     OK      OK       -

Best regards,

                         Krzysztof Olêdzki