Implement support for defining custom channels in the channels{} construct in lexer grammars (fixes #309)
Place error 160 in the correct order in ErrorType.java
Merge pull request #694 from sharwell/fix-309

Implement channels{} block
add parrt summary of conversation with Sam about precedence DFA optimization
Merge pull request #695 from parrt/prec-filter-comments

add parrt summary of conversation with Sam about precedence DFA optimization