autoconf: use AC_PROG_YACC/LEX

Needed for automake. Using AC_PROG_PATH(bison/flex) causes automake to
fail to build .y and .l files.

It is up to the builder to use bison/flex instead of yacc/lex.

Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Matt Turner <mattst88@gmail.com>
diff --git a/bin/.gitignore b/bin/.gitignore
index 3b3f168..5cf62d9 100644
--- a/bin/.gitignore
+++ b/bin/.gitignore
@@ -1,2 +1,3 @@
 /depcomp
 /missing
+ylwrap