TeX4ht support

[michal-h21]

This fix should remove an error message when TeX file that uses embedfile is compiled by TeX4ht, as reported here.

[u-fischer]

I have no problems with it. But it would be perhaps cleaner if embedfile would do

\ifcsname EmFi@Error\endcsname
\else 
\def\EmFi@Error{%
  \@PackageError{embedfile}%
}
\fi

Then you (and other packages) could provide your own definition (which should take two arguments) which then could do nothing, or issue some info.

[michal-h21]

@u-fischer that's another possibility. Should I change my pull request to use this instead?

[u-fischer]

I added it already locally manually and I looked at the other PR too.

[michal-h21]

OK, so we can close this one, I think :)

[u-fischer]

uploaded to ctan as discussed, so closing.

[muzimuzhi]

Is \ifdefined a bit faster than \ifcsname ...\endcsname, especially for unicode engine(s)? LuaTeX Manual, sec. 2.8.3 reads

This [the use of \lastcsname instead of \csname ... \endcsname] is slightly more efficient than constructing the string twice (deep down in LuaTeX this also involves some utf8 juggling), ...

Update: Ah I misunderstood that doc paragraph. Sorry for the noise.