Merged revisions 242521 via svnmerge from

Merged revisions 242521 via svnmerge from
https://origsvn.digium.com/svn/asterisk/trunk

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  r242521 | tilghman | 2010-01-24 00:40:31 -0600 (Sun, 24 Jan 2010) | 15 lines

  Merged revisions 242520 via svnmerge from
  https://origsvn.digium.com/svn/asterisk/branches/1.4

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    r242520 | tilghman | 2010-01-24 00:33:01 -0600 (Sun, 24 Jan 2010) | 8 lines

    Only rebuild bison and flex source files on demand, if bison and flex are detected by the configure script.

    Changed after discussion on the -dev list about possible unnecessary build
    failures, due to checkouts/untars causing these special source files to
    possibly be newer than their resulting C files.  This should additionally
    ensure that nobody need learn about extra Makefile arguments to ensure the
    proper files get rebuilt when changes are made to these special source files.
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.1@242523 65c4cc65-6c06-0410-ace0-fbb531ad65f3