Reduce number of packages install_prereq installs on Debian systems.

'search' will look for any package containing the name provided, so we need to
force a more exact search.
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Merged revisions 379276 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 379277 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@379278 f38db490-d61c-443f-a65b-d21fe96a405b