autoconf version 2.72

[sovhist]

Hello.

Newest Lyx from git can't be compiled on some Linux system because of
nonsupported version of autoconf. 
Error message:

"Using autoconf (GNU Autoconf) 2.72
This autoconf version is not supported by LyX.
LyX only supports autoconf 2.65-2.69, 2.71."

This version of autoconf is actual for Arch Linux and derivatives (I'm
on Manjaro).

Thank you for your work on Lyx, which is wonderfull!

Valdemaras