Kill TreeMap, TreeSet, TrieMap, TrieSet, LruCache and EnumSet

[Gankra]

EnumSet lives on in libcollections so that librustc can still use it. This adds a direct dependency on libcollections to librustc and libserialize.

Should not be merged until rust-lang/rfcs#509 is accepted.

All of these collections have already been moved to collect-rs where they will ideally be maintained and experimented with, or will be replaced by something better: https://github.com/Gankro/collect-rs/

[breaking-change]

r? @aturon @alexcrichton

[killercup]

@gankro I just noticed there are some FIXMEs with refs of rust issue numbers in here (e.g. here). Should those issues be closed or moved to the new repo?

[Gankra]

Those are almost all general language issues, in my experience. e.g. the linked issue (#5244) is just that Variants and [elem, ..n] notation don't play well. We don't log many issues for specific collection flaws. I will update #8009, though.

[alexcrichton]

This looks great, thanks @gankro!

[aturon]

@gankro r=me after rebase/squash

[tbu-]

@gankro You write "Kill EnumSet", but it's still there?

[Gankra]

@tbu- It's not in std anymore; only libcollections.

[pnkfelix]

Hmm I think this PR accidentally destroyed the special \r\n characters that were here:

rust/src/test/run-pass/issue-16278.rs

Lines 15 to 17 in 74ae05a

	fn main() {assert_eq!(b"", b"\
	");
	assert_eq!(b"\n", b"

This breaks the regression testing that we would want for #16278

(I only happened to notice their absence because I was wondering why this file was listed here:)

rust/src/test/run-pass/.gitattributes

Line 2 in f17c230

issue-16278.rs -text