This change improves the way internal APIs are being hidden behind the
`COSMO` define. The cosmo.h header will take care of defining that, so
that a separate define statement isn't needed. This change also does a
lot more to define which APIs are standard, and which belong to Cosmo.
fgets() is now 4x faster which makes Make 2% faster. Landlock Make now
has a builtin $(uniq ...) function that uses critbit trees rather than
functional programming. Since uniq is the most important function this
optimization makes our cold start latency 15% faster.
The `HDRS` and/or `INCS` variables need to be defined in order for
`mkdeps.com` to compute build dependencies for `o//depend`. We're using
INCS here since makeint.h is the evil kind of header that isn't actually
defining a library interface but rather is a hodgepodge of common code.
