Fix character encoding in mmil.raw.html
Fix character encoding in mmil.raw.html

There were some UTF-8 characters in the source file, but that's
not the character encoding we use. So use HTML markup instead.

This problem has been present in mmil.html for some months (it
isn't specific to the .raw.html format).

metamath/set.mm,metamath/set.mm,metamath/set.mm