random: Randomizer::getFloat(): Fix check for empty open intervals (#10185)

* random: Randomizer::getFloat(): Fix check for empty open intervals

The check for invalid parameters for

random: Randomizer::getFloat(): Fix check for empty open intervals (#10185)

* random: Randomizer::getFloat(): Fix check for empty open intervals

The check for invalid parameters for the IntervalBoundary::OpenOpen variant was
not correct: If two consecutive doubles are passed as parameters, the resulting
interval is empty, resulting in an uint64 underflow in the γ-section
implementation.

Instead of checking whether `$min < $max`, we must check that there is at least
one more double between `$min` and `$max`, i.e. it must hold that:

nextafter($min, $max) != $max

Instead of duplicating the comparatively complicated and expensive `nextafter`
logic for a rare error case we instead return `NAN` from the γ-section
implementation when the parameters result in an empty interval and thus underflow.

This allows us to reliably detect this specific error case *after* the fact,
but without modifying the engine state. It also provides reliable error
reporting for other internal functions that might use the γ-section
implementation.

* random: γ-section: Also check that that min is smaller than max

This extends the empty-interval check in the γ-section implementation with a
check that min is actually the smaller of the two parameters.

* random: Use PHP_FLOAT_EPSILON in getFloat_error.phpt

Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>

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Add Randomizer::nextFloat() and Randomizer::getFloat() (#9679)

* random: Add Randomizer::nextFloat()

* random: Check that doubles are IEEE-754 in Randomizer::nextFloat()

*

Add Randomizer::nextFloat() and Randomizer::getFloat() (#9679)

* random: Add Randomizer::nextFloat()

* random: Check that doubles are IEEE-754 in Randomizer::nextFloat()

* random: Add Randomizer::nextFloat() tests

* random: Add Randomizer::getFloat() implementing the y-section algorithm

The algorithm is published in:

Drawing Random Floating-Point Numbers from an Interval. Frédéric
Goualard, ACM Trans. Model. Comput. Simul., 32:3, 2022.
https://doi.org/10.1145/3503512

* random: Implement getFloat_gamma() optimization

see https://github.com/php/php-src/pull/9679/files#r994668327

* random: Add Random\IntervalBoundary

* random: Split the implementation of γ-section into its own file

* random: Add tests for Randomizer::getFloat()

* random: Fix γ-section for 32-bit systems

* random: Replace check for __STDC_IEC_559__ by compile-time check for DBL_MANT_DIG

* random: Drop nextFloat_spacing.phpt

* random: Optimize Randomizer::getFloat() implementation

* random: Reject non-finite parameters in Randomizer::getFloat()

* random: Add NEWS/UPGRADING for Randomizer’s float functionality

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