Re: upcase-region changes 'i' to 'P'

[Richard M. Stallman]

      When I look at (standard-case-table) I see a
    sequence which looks as if it is used for converting to uppercase,
    containing the following subsequence: 65 66 67 68 69 70 71 72 331856
    74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90.  The 331856 should
    be a 73 to yield an 'I', but I don't understand the code which
    initializes this table, nor do I understand the overall structure of
    the table, so I don't know how it gets this value.

This looks like it's in a mode designed for Turkish, turning i into
capital I-with-dot.  Meanwhile, capital I corresponds to lower-case
dotless i.

You must have done something that enabled this mode.  What was it?
(I am not sure how one is supposed to enable it.)