ParserAbstract: remove undefined class in `use`

Class `PhpParser\Parser\Tokens` not exists in current version

Add additional upgrading notes for pretty printer

Improve heuristic for escaping in single quoted strings

It is idiomatic to not escape backslashes if they are followed by
a non-special character.

Don't force newline after doc string when targeting PHP >= 7.3

Add additional test case for assignment precedence

This is a case where the parentheses around the assignment *are*
important.

Avoid repeatedly downloading archive in run-php-src.sh

When doing local testing, chances are that the archive is already
present.

Treat assignments as unary operators

Assignment expressions can be viewed as unary operators where
the whole "$x =" part is the operator.

Remove inc/dec from precedence map

Inc/dec are primitive expressions that only accept a variable
operand, rather than a general expression operand.

Add a phpVersion option to the pretty printer

This is currently just used to initialize the default for short
array syntax.

The default target version in 7.0, which also means t

Add a phpVersion option to the pretty printer

This is currently just used to initialize the default for short
array syntax.

The default target version in 7.0, which also means that the
default for short arrays is flipped to on.

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Add PhpVersion class

Add visibility modifiers to constants

Closes GH-848.

Add __serialize/__unserialize to ClassMethod::$magicNames

Single blank line at eof

A PHP file without end tag must always end with a single empty line feed.

No superfluous elseif

Replaces superfluous elseif with if.

Nullable type declaration for default null value

Adds ? before type declarations for parameters with a default null value

No unused imports

Unused use statements must be removed.

Short scalar cast

Cast (boolean) and (integer) should be written as (bool) and (int), (double) and (real) as (float), (binary) as (string).

Add Parser::getLexer() method

Not sure if this is going to stick, but for now this makes it
easier to obtain the Lexer instance when creating the parser via
ParserFactory.

Add PHP 8 parser with correct concatenation precedence

The PHP 7 and PHP 8 parsers use the same grammar file and only
differ in token precedence.

Move Tokens::T_* to Php7::T_*

Drop the separate tokens class, move them into the parser.

Move token mapping from lexer to parser

This allows a different token mapping per parser.

Move definition of compatibility tokens into separate file

Handle true/false/null types in builder APIs

Add support for true type

The null/false types were alread accepted previously, even though
they are only legal as standalone types since PHP 8.2.

Rename Expr\ClosureUse -> ClosureUse

This is not a real expression, treat it similarly to Node\Arg
or Node\Param.

The old name is retained as an alias for compatibility.