Bug#1095538: xemacs21: Uses autoconf2.13 which is being remove from Debian

[Jeremy Bícha]

Source: xemacs21
Version: 21.4.24-12
Severity: serious
Control: block 1081135 by -1

xemacs21 uses autoconf2.13 which is ancient and is being removed from Debian.

Please switch to autoconf instead.

Thank you,
Jeremy Bícha