[tex-live] Make the extensions for formats different for each engine.

[Olaf Weber]

Right now pdftex uses .fmt for its formats (e.g., latex.fmt) just as
tex does.  Similar for pdfetex and etex, which both use .efmt.  I
don't believe this is a desirable situation, and would like to change
this, possible so that

      tex      -> .fmt
      etex     -> .efmt
      pdftex   -> .pfmt
      pdfetex  -> .pefmt
      pdfxtex  -> .xfmt (could be made .pxfmt for "consistency")
      omega    -> .oft (could be made .ofmt)
      eomega   -> .eoft (could be .eofmt, but who cares)
      aleph    -> .afmt

I know that if you reduce the extension to three letters, you get
overlaps with .pfm, .ofm, .afm.  The one place this actually matters
is kpsewhich, where I've resolved this by ensuring that the mapping of
file extension to kpse_file_format_t looks at kpse_format_t last.

Thoughts?

-- 
Olaf Weber

               (This space left blank for technical reasons.)