[Buildbot] #3557: add option to join stdout and stderr for ShellCommand

[Buildbot trac]

#3557: add option to join stdout and stderr for ShellCommand
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Reporter:  kparal       |       Owner:
    Type:  enhancement  |      Status:  new
Priority:  major        |   Milestone:  0.9.+
 Version:  master       |  Resolution:
Keywords:               |
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Changes (by rutsky):

 * milestone:  undecided => 0.9.+


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Ticket URL: <http://trac.buildbot.net/ticket/3557#comment:1>
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