Fixed NPE during error recovery.

As indicated in https://github.com/antlr/grammars-v4/issues/113 the custom code responsible for token creation causes a NPE to be thrown when the parser tries to recover from errors.

This change contains two fixes:

1. custom created tokens now also get start- and stop-indexes, channel, etc.
2. original indentation spaces and line break chars are kept in the custom created token