Make configure accept both lex _and_ flex.

git-svn-id: svn://katsu.triplehelix.org/dgamelaunch/trunk@514 db0b04b0-f4d1-0310-9a6d-de3e77497b0e

TODO

@@ -1,3 +1,4 @@
+-whenever config file has a dir, check that it ends with "/"
 -in domailuser(), we need find_curr_player_game(username)
 -for menu definitions, allow "default" commands (when user presses a
  key not defined in other commands):

configure.ac

@@ -11,7 +11,7 @@ AC_PROG_CC(cc gcc)
 AC_STDC_HEADERS
 
 AC_PROG_LEX
-if test "x$LEX" != xflex; then
+if test -z "$LEX"; then
    AC_MSG_ERROR([lex or flex not found.])
 fi