AppVeyor: fix fork() on 32 bit cygwin in shell module.
AppVeyor: fix fork() on 32 bit cygwin in shell module.

[2015-10-31 22:44:22.609963] (user/test) CLI -> ZNC [PRIVMSG *shell :echo blahblah]
      0 [main] znc 2624 child_info_fork::abort: address space needed by 'simple_away.so' (0x380000) is already occupied
[2015-10-31 22:44:22.618538] (user/test) ZNC -> CLI [:*shell!shell@/home/appveyor PRIVMSG nick :Failed to execute: Resource temporarily unavailable]

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