[Bug #20654]

This commit fixes Integer#ceil and Float#ceil when the number is
negative and ndigits is large such that 10**ndigits is a bignum.

Previously, it would return 0 in such cases. However, this would cause
unexpected behaviour such as:

    puts 1.ceil(-5) # => 100000
    puts 1.ceil(-10) # => 10000000000
    puts 1.ceil(-20) # => 0

This commit changes the last result so that it will return
100000000000000000000.

[Bug #20654]

This commit fixes Integer#floor and Float#floor when the number is
negative and ndigits is large such that 10**ndigits is a bignum.

Previously, it would return 0 in such cases. However, this would cause
unexpected behaviour such as:

    puts -1.floor(-5) # => -100000
    puts -1.floor(-10) # => -10000000000
    puts -1.floor(-20) # => 0

This commit changes the last result so that it will return
-100000000000000000000.

	[Bug #19323] Raise `RangeError` instead of integer overflow

	---
	 bignum.c                  |  5 ++++-
	 test/ruby/test_integer.rb | 18 ++++++++----------
	 2 files changed, 12 insertions(+), 11 deletions(-)

The methods aren't called for FIXNUM, and it's best to have
consistent behavior.

Fixes [Bug #18377]

This speeds up performance by multiple orders of magnitude for
large integers.

Fixes [Bug #14391]

Co-authored-by: tompng (tomoya ishida) <tomoyapenguin@gmail.com>

The error message has an integer overflow because it treats an unsigned int as a signed int.

Before:
```
> 3_000_000_000.chr
-1294967296 out of char range (RangeError)
```

After:
```
> 3_000_000_000.chr
3000000000 out of char range (RangeError)
```

Redmine ticket: https://bugs.ruby-lang.org/issues/17186

`Integer.sqrt(0xffff_ffff_ffff_ffff ** 2)` caused assertion failure
because of integer overflow.  [ruby-core:95453] [Bug #16269]