6.10.0: Target runtimes

• Implemented feature request #123: Use php:X.Y instead of PHP.X.Y
  for target runtimes. The older syntax is still supported!
  (@thekid)

6.9.0: Readonly properties

• Merged PR #124: Add support for readonly properties. Implements feature
  request #115, using native code for PHP 8.1 and simulated via virtual
  properties for PHP 7.X and PHP 8.0
  (@thekid)

6.8.3: Promoted property types fix

• Fixed types not being emitted for promoted properties - @thekid

6.8.2: Extraneous operators fix

• Fixed Call to undefined method ...::emitoperator()) which do not
  provide any context as to where an extraneous operator was encountered.
  (@thekid)

6.8.1: Enum constants fix

• Fixed issue #122: Undefined constant Sources::FromEmpty (when using
  PHP 8.1 native enumerations in PHP 8.0 and lower and the JIT compiler)
  (@thekid)

6.8.0: Intersection types

• Merged PR #120: Support for PHP 8.1 intersection types, accessible via
  reflection in all PHP versions, and runtime type-checked with 8.1.0+
  (@thekid)

6.7.0: Native callable syntax

• Changed emitter to omit extra newlines between members, making line
  numbers more consistent with the original code.
  (@thekid)
• Merged PR #114: Implements first-class callable syntax: strlen(...)
  now returns a closure which if invoked with a string argument, returns
  its length. Includes support for static and instance methods as well as
  indirect references like $closure(...) and self::{$expression}(...),
  see https://wiki.php.net/rfc/first_class_callable_syntax
  (@thekid)

6.6.0: Performance, code coverage improvements

• Emit null-coalesce operator as $a ?? $a= expression instead of as
  $a= $a ?? expression, saving one assignment operation for non-null
  case. Applies to PHP 7.0, 7.1 and 7.2.
  (@thekid)
• Removed conditional checks for PHP 8.1 with native enum support, all
  releases and builds available on CI systems now contain it.
  (@thekid)
• Increased test coverage significantly (to more than 90%), especially
  for classes used by the compiler command line.
  (@thekid)

6.5.0: Declare directives

• Merged PR #111: Add support for directives using declare - @thekid

6.4.0: Never return type

• Merged PR #110: Rewrite never return type to void in PHP < 8.1, adding
  support for this PHP 8.1 feature. XP Framework reflection supports this
  as of its 10.10.0 release.
  (@thekid)