PHP 8 ready

Tested to work under PHP 8.

Enhanced exception context, fixed PCRE issue

Kudos to @ohader for pointing at these issues, and providing fixes:

• hoaproject/Compiler#111
• hoaproject/Compiler#112
• hoaproject/Compiler#113

Fix parsing of spaces in LL(k) token definitions

See #3

Initial release

This version should be input-output-wise backward-compatible with the original package.

BC breaking changes include:

• Hoa\Exception\Exception sub-classes are no longer thrown, please switch to Hoa\Compiler\Exception
• The package itself does not depend on development time only dependencies. If you need to call getAST() you need to manually install hoa/regex and hoa/file.

Other major changes:

• Tests now also use PHPUnit.