Documentation fix - waitfordialtone is not boolean, it's time in milliseconds

Documentation fix - waitfordialtone is not boolean, it's time in milliseconds

Changing text in chan_dahdi.conf sample to be accurate.

(issue ASTERISK-22308)
(closes issue ASTERISK-22308)
Reported By: Malcolm Davenport
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Merged revisions 398880 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 398881 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 398882 from http://svn.asterisk.org/svn/asterisk/branches/12

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@398883 65c4cc65-6c06-0410-ace0-fbb531ad65f3