removed vhdl standard due to copyright
added notes on used standards
added lexer.vhd that tests lexical analysis

The VHDL-2000 standard has an entire clause covering the lexical components of the
language. It allows for rather weird character replacements, e.g. string literals
%hello% instead of "hello". If we opt for a fully compliant parser, we need to take
these things into account.
VHDL lexer is improving

Things are fairly fleshed out as of now. No error reporting is implemented yet, but
it should be possible to lex every VHDL source file out there. Next up is tagging
identifiers which are reserved keywords with a special token type, such that the
parser may operate on them as quickly as possible.
added KeywordMapper

A simple helper class that matches a string against a set of keywords as efficiently
as possible and returns an ID for it. The current implementation is based on a
modified binary search, which is fairly efficient but gets into trouble if one takes
VHDL's case-insensitivity into account.
started working on unicode case folding