Fix BASHisn in test for raptor version: use -lt for string less than

Author: dajobe

configure.ac

@@ -441,7 +441,8 @@ RAPTOR_VERSION_DEC=`echo $RAPTOR_VERSION | $AWK -F. '{printf("%d\n", 10000*$1 +
 AC_SUBST(RAPTOR_VERSION_DEC)
 AC_SUBST(RAPTOR_MIN_VERSION)
 
-AM_CONDITIONAL(RASQAL_SORT, test $RAPTOR_VERSION_DEC '<' 20015)
+# String comparison: -lt is portable (ksh, bash) but '<' is bash
+AM_CONDITIONAL(RASQAL_SORT, test $RAPTOR_VERSION_DEC -lt '20015')
 
 dnl Checks for regex libraries
 have_regex_pcre=0