[Tex] Change *.mtc0 to *.mtc[0-9] *.mtc[1-9][0-9]

>`\@tocfile`
The name of the file containing the minitoc is constructed from `\jobname` and a suffix `\@tocfile`, which is `.mtc` (long extensions) or `.M` (short extensions) followed by the absolute number of the minitoc.

```
\if@mtc@longext@
  \def\@tocfile{mtc\The@mtc}%
\else
  \def\@tocfile{M\The@mtc}%
\fi
```