As the Summer of Code project should be "developed in public",
I can't wait with committing until everything works.
Therefore, import the beginnings of the C# parser into SVN.

The parser itself is currently just a skeleton, but the lexer is pretty
complete already. It only misses out on two things at the moment:

- Dealing with those ominous "non-keyword identifiers
that have a special meaning in the grammar"
(see http://www.jaggersoft.com/csharp_standard/9.4.3.htm).
I'll come back to this when I get to tackle them in the grammar.

- Filtering out pre-processor directives.
It's easier than in C++, because there are no text replacements,
only selective "turning on and off" for #if'd sections.
Not completely trivial though, but I already have a good idea
for how to cope with it, just need to implement it.
That's the upcoming task now.