[Lexer] Removed some duplicated code related to the opening and closing chars in literals like %(...), %[...], %w{...}, etc.

[Lexer] Adds support for extra delimiters in %w and %i

All of the pairs [], {}, () and <> can be used to delimit string and
symbol array with the %w and %i notation, respectively.

Adds HTML::EscapedString

Added: IPv6, UDP and UNIX sockets

Fix: pthread_exit leaks memory

As per the man page , pthread_exit may be run before
pthread_cleaned_push have been popped, which may result in memory
leaks —Valgrind indeed complains about it. Returning from a Thread
is supposed to be a preferable solution.

That also fixes #352 since we no longer have pthread_exit forcing an
unwind.

The compiler can now be compiled again!

Fixed an issue with how bools are stored in unions (it has 64 bits hardcoded, which was wrong in any case). Related to #350

Fixed: moved the "can't cast to T because it was never instantiated" error from compile-time to runtime

[Hashes] Adds a comparator and changes the initializers a bit