Remove unused variable 'tmp' from helpfun in ilbc codec

gcc version 4.6.2 caught an unused variable in the ilbc codec
library.  This would prevent compilation with --enable-dev-mode;
variable removed.
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Merged revisions 351760 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 351761 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@351763 65c4cc65-6c06-0410-ace0-fbb531ad65f3