ebnf.py, examples/FixedEBNF, examples/FlexibleEBNF: directive can now contain grammar expressions, next to regular expressions, symbols and literals

ebnf.py: Automatic reordering of string literals in badly ordered Alternative (i.e. 'ID' | 'IDREF' => 'IDREF' | 'ID')

compile.py: better error message when fallback_compiler()-method fails; ebnf.py: added on_ZOMBIE__()-method to better handle faulty syntax-trees.

scripts/dhparser.py - now uses XXXParser.py rather then XXXCompiler.py as default file-name for the translator

- configuration presets refactored in order support multiprocessing start methods "spawn" and "fork-server"

- examples: replaced "report=True" with "report='REPORT'" when calling testing.grammar_suite in all tst_*.py-scripts