snort: fix m4 causes out of memory during configure

There is an incorrect m4_define() in configure.in which will result in an
infinite recursion, and it doesn't make sense, since snort 2.9.7 it has been
commented out. We follow this solution to fix it.

Signed-off-by: Zhiquan Li <zhiquan.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>