Updated most of Kernel module methods

[sampersand]

This PR updates most of Kernel's module methods. Here's some things to note:

1. Only Complex, Rational, open, rand, select, exec, spawn, and system remain. These methods will be addressed in later PRs, but are somewhat complicated, and I wanted to get this PR merged.
2. There is one TODO that's still outstanding that will be completed by the time I finish the other Kernelmethods: The new assert_send_raises doesn't actually validate the signature it's passed (instead, it only validates the raised error).
3. The def self?.XXX syntax is used to indicate module_functions. However, it doesn't mark the instance methods as private (it should be equal to def self.XXX and private def XXX).
4. An issue I ran into while doing this is that loop with no arguments returns an Enumerator, except the each method doesn't actually pass in any arguments (ie loop.each{|*x,**y,&z| break [x, y, z] } gives you [[], {}, nil). This means the Enumerator[nil, untyped] interface is technically incorrect, as that implies it is given an argument. I've omitted the test, but I'm not sure what to do about it.