MEDIUM: config: Dynamic sections.

This patch permit to register new sections in the haproxy's
configuration file. This run like all the "keyword" registration, it is
used during the haproxy initialization, typically with the
"__attribute__((constructor))" functions.
diff --git a/include/common/cfgparse.h b/include/common/cfgparse.h
index dcc4003..106bad7 100644
--- a/include/common/cfgparse.h
+++ b/include/common/cfgparse.h
@@ -70,6 +70,8 @@
 void init_default_instance();
 int check_config_validity();
 int str2listener(char *str, struct proxy *curproxy, struct bind_conf *bind_conf, const char *file, int line, char **err);
+int cfg_register_section(char *section_name,
+                         int (*section_parser)(const char *, int, char **, int));
 
 #endif /* _COMMON_CFGPARSE_H */