Consider linux-gnuspe as linux-gnu

* The powerpcspe Linux port uses linux-gnuspe as the OS string.
* Our build system shouldn't really care for that, so just call it linux-gnu.
* Original report: Roland Stigge , http://bugs.debian.org/701505

Review: https://reviewboard.asterisk.org/r/2357/
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Merged revisions 382110 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 382111 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@382113 65c4cc65-6c06-0410-ace0-fbb531ad65f3