Enforce "gdb" in GDB/MI prompt.
Add comment and test show tuples do not need keys.
Remove the ability to print the parse tree.

This functionality has no purpose in the library at this point.
I thought at one point it would be useful for unit testing but
I decided against using it for this purpose.

Then I thought it might be useful for debugging. However, now
it's easy to print a GDB/MI line and the token at which it is an error.

Dropping support for this functionality until it becomes necessary again.
Remove roadmap.txt from distribution.
Remove execute permission on gdbmi_grammar.y
Remove the logging interface for now.

I've decided to move the logging interface up to the client level.
Each user of gdbwire can log how they see fit.

I will need to add the logger callback function for the client
after I write the main client interface.