we don't need LEX anymore

diff --git a/configure.in b/configure.in
index 8076c34..94bc240 100644
--- a/configure.in
+++ b/configure.in
@@ -8,7 +8,6 @@
 AC_PROG_CC
 AC_PROG_INSTALL
 AC_PROG_RANLIB
-AM_PROG_LEX
 
 dnl checks for libraries