Merged revisions 134649 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

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r134649 | tilghman | 2008-07-30 16:38:50 -0500 (Wed, 30 Jul 2008) | 4 lines

Qwell pointed out, via IRC, that the previous fix only worked when explicitly
set.  When nothing is set, and the option is implied, it breaks, because
configure sets the prefix to 'NONE'.  Fixing.

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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@134650 65c4cc65-6c06-0410-ace0-fbb531ad65f3