configure.ac: utilize wide columns for summary

configure.ac

@@ -3993,12 +3993,13 @@ AS_IF([test "$silent" = yes], [], [
 AS_IF([${FOLD+:} false], [], [
 AS_IF([test "`echo abcdefg hijklmno | fold -s -w10 | sed 1d`" = hijklmno], [FOLD="fold"], [FOLD=])
 ])
+fold_width=`expr $COLUMNS - 30 2>/dev/null` || fold_width=50
 AS_REQUIRE_SHELL_FN([config_summary],
     [AS_FUNCTION_DESCRIBE([config_summary], [NAME, VAL], [configuration summary])],
     [AS_IF([test -z "$2"], [], [
 	AS_ECHO_N(["   * $1:                     "]) | dd bs=1 count=26 2>/dev/null
 	AS_IF([test "$FOLD"], [
-	    echo "$2" | fold -s -w50 |
+	    echo "$2" | fold -s -w$fold_width |
 	    sed '1!s/^/                          /;$!s/$/\\/'
 	], [echo "$2"])
     ])]