MINOR: cfgparse: suggest correct spelling for unknown words in global section

MINOR: cfgparse: suggest correct spelling for unknown words in global section

The global section also knows a large number of keywords that are not
referenced in any list, so this needed them to be specifically listed.
It becomes particularly handy now because some tunables are never easy
to remember, but now it works remarkably well:

  $ printf "global\nsched.queue_depth\n" | ./haproxy -c -f /dev/stdin
  [NOTICE] 070/093007 (23457) : haproxy version is 2.4-dev11-dd8ee5-24
  [NOTICE] 070/093007 (23457) : path to executable is ./haproxy
  [ALERT] 070/093007 (23457) : parsing [/dev/stdin:2] : unknown keyword 'sched.queue_depth' in 'global' section; did you mean 'tune.runqueue-depth' maybe ?
  [ALERT] 070/093007 (23457) : Error(s) found in configuration file : /dev/stdin
  [ALERT] 070/093007 (23457) : Fatal errors found in configuration.