[tex-k] Typos in METAFONT's help messages

[胡亚捷 (Hu Yajie)]

1. The primitive `fontinfo' is now called `fontdimen', but the old name still
persists in a help message produced by METAFONT:

    *fontdimen 1;
    ! Missing `:' has been inserted.
    [...]
    ? H
    A colon should follow a headerbyte or fontinfo location.

and also in two comments in section 1096 of Volume D.

2. When you say "ligtable 1;" and type "H" to the error message, METAFONT says
"I was looking for `=:' or `kern' here." But the set of ligature ops has been
extended far beyond "=:".

3. When you say "numeric whatever[];" and type "H", to the error message,
METAFONT says "You can't use, e.g., `numeric foo[]' after `vardef foo'."
The "use" should probably be "say".

4. When you say "def a;" and type "H" to the error message, METAFONT says
"The next thing in this `def' should have been `='," but when you say
"for a;" and type "H", the response is "The next thing in this loop
should have been `=' or `:='." The two help messages seem inconsistent.
(On the other hand, the response to "let a;" is "You should have said
`let symbol = something'." The wording makes it difficult to mention ":=".)

5. The help message for interrupts is "Try to insert some instructions for me
(e.g.,`I show x'),". A space is apparently missing after the comma.

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Previous reports:
https://github.com/dine2014/texbook-mfbook-bugs/blob/master/bugs.md