lexan: add a label to CharLocation to hold extra info e.g. the source file name.
This will be essential if support for injecting/including files into the input
stream is included.  But for the moment it just makes error reporting easier.

Signed-off-by: Peter Williams <pwil3058@gmail.com>
symbols: reduce names stating with "dd" etc to a non fatal issue.
D's detection of shadowed identifiers should make this safe as any conflicts
won't slip through undetected.

Signed-off-by: Peter Williams <pwil3058@gmail.com>
symbols: fix bug in contract caused by previous change

Signed-off-by: Peter Williams <pwil3058@gmail.com>
bespoke: strip decoration off token field name declaration

Signed-off-by: Peter Williams <pwil3058@gmail.com>
grammar: remove assertion for states' non empty look ahead sets -> error
This needs to become a reportable error as it is caused by an erroneous
specification and is not a sign of logic failure.

Signed-off-by: Peter Williams <pwil3058@gmail.com>
specification: update dunnart's language specification for lessons learnt
implementing the bespoke version.

Signed-off-by: Peter Williams <pwil3058@gmail.com>