Configuration for YouCompleteMe[1] is developer's configuration, no
need to have it inside the repository.

[1] https://github.com/ycm-core/YouCompleteMe

Many data structures had wrong spacing when outputting with operator<<
for the data structure. For example, see the missing space between
content and alphabet in string::LinearString.

 (LinearString content = [a, a, c, c, a]alphabet = {a, c})

Let's fix that, it bothered me for quite a long time.

Extended tree patterns feature node wildcards representing any label in the
match of the pattern in the corresponding node