[Bug #20030] dispatch invalid escaped character without ignoring it

	[Bug #19924] Source code should be unsigned char stream

	Use `peekc` or `nextc` to fetch the next character, instead of reading
	from `lex.pcur` directly, for compilers that plain char is signed.
	---
	 parse.y                 | 10 +++++-----
	 test/ruby/test_parse.rb |  2 ++
	 2 files changed, 7 insertions(+), 5 deletions(-)

	Handle unterminated unicode escapes in regexps

	This fixes an infinite loop possible after ec3542229b29ec93062e9d90e877ea29d3c19472.
	For \u{} escapes in regexps, skip validation in the parser, and rely on the regexp
	code to handle validation. This is necessary so that invalid unicode escapes in
	comments in extended regexps are allowed.

	Fixes [Bug #19750]

	Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
	---
	 parse.y                 | 97 ++++++++++++++++++++++++++++++++-----------------
	 test/ruby/test_parse.rb | 16 ++++++++
	 2 files changed, 79 insertions(+), 34 deletions(-)

```
test/ruby/test_parse.rb:1384: warning: assigned but unused variable - obj
test/ruby/test_pattern_matching.rb:1162: warning: unused literal ignored
test/ruby/test_pattern_matching.rb:1165: warning: unused literal ignored
test/ruby/test_pattern_matching.rb:1161: warning: assigned but unused variable - a
test/ruby/test_pattern_matching.rb:1164: warning: assigned but unused variable - b
```

And a newline should be significant here.

block to another method without having to provide a name for the
block parameter.

Implements [Feature #11256]

Co-authored-by: Yusuke Endoh mame@ruby-lang.org
Co-authored-by: Nobuyoshi Nakada nobu@ruby-lang.org