[Automake-NG] Removing support for DOS, DJGPP and Windos < 2000 in Automake-NG

[Stefano Lattarini]

Hello automakers.

As part of the general de-crufting of Automake-NG, I'd like to remove support 
for
MS-DOS, DJGPP and older Windows.  But of course, I'd rather not cause 
regressions
in MinGW support while ding so.

So I'd like to know answers to the following questions with certainty:

  1) Are filenames starting with a dot portable to MinGW and modern Windows
     systems (i.e., Windows 2000 or later)?

  2) Can we transparently use and handle files which are not unique according
     to the 8+3 limit (8 characters for file name, 3 for the file extension)?

If I read the Autoconf manual (section "File System Conventions") correctly,
the answer to both questions is "yes", but I'd rather double check here, in
case some Windows/MinGW expert has something to add.

Regards,
  Stefano