Fix ordinal() suffix for negative numbers

[yu2971512385-ui]

Problem

ordinal() gives every negative number the th suffix:

>>> import humanize
>>> humanize.ordinal(-1)
'-1th'
>>> humanize.ordinal(-3)
'-3th'
>>> humanize.ordinal(-21)
'-21th'

The docstring says the function "works for any integer or anything int() will turn into an integer", and negative integers already reach the suffix table — they just index it with the wrong digit.

Root cause

digit = 0 if value % 100 in (11, 12, 13) else value % 10

Python's % returns a non-negative remainder for a negative left operand, and that remainder belongs to a different digit: -1 % 10 == 9, -3 % 10 == 7, -21 % 10 == 9. Every one of those lands on a th entry, so the bug is invisible except that the answer is always th.

Fix

Index the table with the last digits of the magnitude. The 11/12/13 exception keeps working because it is applied to the same magnitude:

>>> humanize.ordinal(-1), humanize.ordinal(-2), humanize.ordinal(-3)
('-1st', '-2nd', '-3rd')
>>> humanize.ordinal(-11), humanize.ordinal(-12), humanize.ordinal(-13)
('-11th', '-12th', '-13th')
>>> humanize.ordinal(-21), humanize.ordinal(-111)
('-21st', '-111th')

Positive values, non-numeric input and the non-finite handling are untouched.

This matches how the module already treats signs elsewhere — intword(-1500000) → '-1.5 million' and fractional(-1.3) → '-1 3/10' both keep the sign on the number and format the magnitude.

Tests

Nine negative cases added to the existing test_ordinal parametrisation, covering the plain digits, the 11/12/13 exception and a value past 100. Verified they fail before the change (4 failed, 246 passed) and pass after (250 passed).

[hugovk]

Duplicate of #405 and #321 and lots more.

Check for duplicates next time.