Implemented `system` and `backtick` using `exec`. Removed the ugly `system2`.
Some refactors
If a call in an initialize passes "self", instance vars coming afterwards are now marked as nilable
Allow using backtick in macros (same as system)
Missing changes
Updated Changelog
Added IO#tty?
Fixed String#chomp
Added IO#each_line
Use C.system on compiler --run until we fix it
Special treatment for IO#puts(String): don't print a newline if the string already ends in one