[PATCH] ax_prog_flex: avoid use of grep empty string escape extension

Lets the test work with OpenBSD grep.
---
 m4/ax_prog_flex.m4 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git m4/ax_prog_flex.m4 m4/ax_prog_flex.m4
index 57b7960..a3489f3 100644
--- m4/ax_prog_flex.m4
+++ m4/ax_prog_flex.m4
@@ -42,14 +42,14 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 10
+#serial 11
 
 AC_DEFUN([AX_PROG_FLEX], [
   AC_REQUIRE([AM_PROG_LEX])
   AC_REQUIRE([AC_PROG_EGREP])
 
   AC_CACHE_CHECK([if flex is the lexer generator],[ax_cv_prog_flex],[
-    AS_IF([$LEX --version 2>/dev/null | $EGREP -q '^\<flex\>'],
+    AS_IF([$LEX --version 2>/dev/null | $EGREP -qw '^flex'],
       [ax_cv_prog_flex=yes], [ax_cv_prog_flex=no])
   ])
   AS_IF([test "$ax_cv_prog_flex" = "yes"],
-- 
1.8.5.3