math: fix division with negative numbers (fix #19585)

[yuyi98]

This PR fix division with negative numbers (fix #19585).

• Fix division with negative numbers.
• Add test.

import math.big

fn main() {
	// Correct: 123
	r1 := big.integer_from_int(1234) / big.integer_from_int(10)
	println(r1)
	assert '${r1}' == '123'

	// Incorrect: -124
	r2 := big.integer_from_int(-1234) / big.integer_from_int(10)
	println(r2)
	assert '${r2}' == '-123'

	// Correct: -123
	r3 := big.integer_from_int(1234) / big.integer_from_int(-10)
	println(r3)
	assert '${r3}' == '-123'

	// Incorrect: 124
	r4 := big.integer_from_int(-1234) / big.integer_from_int(-10)
	println(r4)
	assert '${r4}' == '123'
}

PS D:\Test\v\tt1> v run .
123
-123
-123
123