Alias syntax removal

[bearophile]

Now I have a good amount of code broken by:

alias x = 5;
alias this = foo;

I don't expect all changes of a beta to be kept in a final 
compiler version, but I think the removal of a syntax should be 
announced (and discussed) in this newsgroup (if the removal of 
such syntax was discussed in this newsgroup, then I have missed 
it):

https://github.com/D-Programming-Language/dmd/issues/1413

Bye,
bearophile