Switching from Automake to GNU Make

[Paul Eggert]

Bug#26100 contains a patch to change the Emacs build procedure to use 
GNU Make instead of Automake, to help simplify and streamline the 
procedure (since we already assume GNU Make). The patch is designed to 
be portable, and I've tested it on Fedora and Solaris. This email is a 
heads-up to people who build on other platforms, since it'll be less 
disruptive if we can iron out any kinks before installing the patch in 
master.