Update remaining references to old package name
Fixing some types

int_fast8_t might be a type wider than 8 bits, in which case the compiler may decide that
the unsigned value of 'code' can be represented in that signed type, thus instead of
getting a negative number we get a positive one, which then screws up computation
totally.

Also use the fastest types for 'length' and 'offset' that are at least 16 bits wide.
Add reference to comment

Apparenty this feature is either only planned or not available in every TTD version.
Use native path separators

Windows tools don't like forward slashes on the command line, they parse them
as argument separators. However, in makefiles they are understood correctly as
path separators.
More file extensions ignored
Let's just use the ASCII charater set

Not all terminals understand UTF-8, and they make messages unreadable.
Merge available fixes