Fixed duplicated warning

	As `command_rhs` is always a "value expression", `command_asgn`
	does not need the same check.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67868 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	Do not turn on keyword_init for Struct subclass if keyword hash is
	 empty

	This was accidentally turned on because there was no checking for
	Qundef.

	Also, since only a single keyword is currently supported, simplify
	the rb_get_kwargs call.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67866 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	`Regexp` in `MatchData` can be `nil`

	`String#sub` with a string pattern defers creating a `Regexp`
	until `MatchData#regexp` creates a `Regexp` from the matched
	string.  `Regexp#last_match(group_name)` accessed its content
	without creating the `Regexp` though.  [Bug #16508]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67865 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	time.c (find_time_t): fix round-to-zero bug

	`find_time_t` did not work correctly for year older than the Epoch
	because it used C's integer division (which rounds negative to zero).

	For example, `TIme.new(1933)` returned a wrong time whose year is 1922
	in Asia/Kuala_Lumpur because there is no 00:00:00 1st Jan. 1933 in the
	time zone.

	```
	$ TZ=Asia/Kuala_Lumpur ruby -e 'p Time.new(1933)'
	1932-12-31 00:00:00 +0700
	```

	This change fixes the issue by using `DIV` macro instead of `/`.
	Now `Time.new(1933)` returns a time in 1933.

	```
	$ TZ=Asia/Kuala_Lumpur ruby -e 'p Time.new(1933)'
	1933-01-01 00:20:00 +0720
	```

	[Bug #16159]

	Added a test for [Bug #16159]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67864 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	marshal.c: check instance variable count

	* marshal.c (w_obj_each): ensure that no instance variable was
	  added while dumping other instance variables.  [Bug #15968]

	Hoisted out w_ivar_each


	marshal.c: check instance variable count

	* marshal.c (w_ivar_each): ensure that no instance variable was
	  removed while dumping other instance variables.  [Bug #15968]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67861 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Fix for wrong fnmatch patttern

* dir.c (file_s_fnmatch): ensure that pattern does not contain a
  NUL character.  https://hackerone.com/reports/449617


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67809 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67778 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	Fixed heap-use-after-free
	
	* string.c (rb_str_sub_bang): retrieves a pointer to the
	  replacement string buffer just before using it, for the case of
	  replacement with the receiver string itself.  [Bug #16105]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67773 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	UTF LE is fixed at least the first 2 bytes
	
	* io.c (io_strip_bom): if the first 2 bytes are 0xFF0xFE, it
	  should be a little-endian UTF, 16 or 32.  [Bug #16099]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67772 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

	array.c: always check frozenness in Array#unshift. Fixes [Bug #15952]

	Closes: https://github.com/ruby/ruby/pull/2251

	array.c add back shared array optimization to
	 ary_ensure_room_for_unshift

	Bug fix in commit ec8e5f5aa64e2a [Bug #15952] disabled an
	optimization in this function.

	Closes: https://github.com/ruby/ruby/pull/2252

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67771 b2dd03c8-39d4-4d8f-98ff-823fe69b080e