bug#20640: 24.5; lexical-binding should work like a normal file-local variable

[Stefan Monnier]

> Even if the code were to check for "coding:" (which we already have to
> scan the end of the file for) and "lexical-binding:" in the same pass?

The check for "coding:" is a misdesign, indeed.  I think we should use
some utf-8 tell-tale sign at the beginning of *.el files to eliminate
the need to check for "coding:" (and to go through
load-with-code-conversion) in the normal case.  It could be a utf-8 BOM
or something like that.  Ideally we could give extra meaning to this
marker so it not only means "uses utf-8" but also "uses
lexical-scoping", so that we can have a future where we don't need to
add "lexical-binding:t" to every file.


        Stefan