Handle multiple `-g` options correctly

[Ulrich Windl]

When using multiple -g options, like in monit -g server -g network status only the last group (network) is selected.

So either:

• Output an error if multiple -g options were found, or
• combine them (“any of”)

Possible enhancement request: Allow flexible combinations of groups, like -g !network meaning everything but group network, -g A -g+B meaning checks in either “group A or group B, -g A -g-B meaning “those checks in group A, but not those in group B ”.

[Tildeslash]

Fix Issue #975: Monit CLI: Monit didn't return any warning if -s, -p, -l, -g or -c command-line options were specified multiple times and silently used the last value only. Monit will generate a warning now. When these options were used multiple times, there was also a minor memory leak (fixed too)

→ <<cset 6828ae6b36b3>>