[icu-design] Proposal: Change ICU4C PluralRules.select(int32_t) to select(double)

[C. Ho (賀. <cla...@go...>]

Hi,
    This is a minor modification corresponding to the new ICU4J API change
Peter proposed on May 20.  The implementation and test is done in my local.
I knew it is late to change the public API, but this one is very minor.  I
am neutral to submit my changes.

This is the description copied from Peter's email:
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In CLDR 1.6 we are trying to extend the plural rules to cover decimal
fractions (since the existing rules do not cover all of the cases; for
example in French, decimal values from 0.0 up to but not including 2.0
take the "one" form, and others take the "other" form, while in
Ukrainian, all non-integer values take the "other" form, which is not
used for any integers.

To support this we need to extend PluralRules.select(long) to take a
double parameter instead. This API is currently marked Draft ICU 3.8
(but this should be a compatible automatic coercion anyway).

Currently the rules include:
 * relation      = is_relation | in_relation | 'n' <EOL>
 * is_relation   = expr 'is' ('not')? value
 * in_relation   = expr ('not')? 'in' range

The proposal is to expand "relation" and define "within_relation" as
follows:
 * relation      = is_relation | in_relation | within_relation | 'n'
<EOL>
 * within_relation   = expr ('not')? 'within' range

An in_relation only includes integers in the specified range; a
within_relation includes all decimal numbers (double values) in the
specified range.

Claire.