bug#26837: Wrong file in "autoloading failed to define" error

[Glenn Morris]

Alex wrote:

>> -    whole_buffer = (PT == BEG && ZV == Z);
>> +    whole_buffer = (BUF_PT (b) == BUF_BEG (b) && BUF_ZV (b) == BUF_Z (b));
[...]
> I can't claim to know what is going on within that function, but your
> patch seems to only work for some files (e.g. your bar.el). If bar
> starts with a comment, then bar isn't moved to the top after evaluating
> (load "bar").

The intent of the code seems to be to only adjust an existing
load-history element for some file if the entire file is being loaded.
I guess in the leading comment case, something else has already moved
point looking for a significant leading comment (eg lexbind, script,
prop-line). Hmmm.