Initial commit.

A basic indentation-based parser.

Missing:

 - any sort of special block
 - efficient/useful generated code
 - locations for errors
 - support for named ASCII escapes and gaps in string literals
 - documentation
 - validity checking

The parser also incorrectly allows the nesting of strings
and attributes without reporting excessive indentation (behaviour,
however, doesn’t change).
Added support for ASCII escape codes and gaps.
Escaped curly braces.

As well as every other character.

Maybe the bug of two years will be addressed in a few more.
Updated categories.