Lets deprecate the length in the arrays index

[Frank Benoit (keinfarbton)]

There was this thread:

22-Oct-2005
It's time to deprecate "array [length]" in favour of "array [$]"

Actually I noticed, i still can use length inside an array index, even
if compiling without -d (deprecated).

For me that means, I do not use the identifier 'length' in D. For
nothing. Because it can happen, it collides with this array stranger.

Please remove this or deprecated this.