Add gar to the check for AR for those silly OSes (Solaris) that don't have ar.

autoconf2.13 couldn't handle AC_PROG_GREP, so I removed it.  This is fine,
since we don't need to use anything that the configure script doesn't.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@259439 65c4cc65-6c06-0410-ace0-fbb531ad65f3