A few non-breaking changes

[nical]

• Add pre/post_transform, deprecate pre/post_mul. This name is less ambiguous: the meaning of pre and post here is really about the semantics of the tranformation and not about the underlying matrix the latter being currently in a confusing step for a number of people.
• Add a default module with type aliases for the default unit. The goal is to rename all TypedFoo types into Foo next time we commit to a breaking change and use default::Foo for the aliases with unknown units.
• Remove unstable must_use annotations. They add noise to the code and aren't very useful since they only work with the nightly compiler and the unstable feature.

The first two changes will let us transition some of the names at our leasure rather than having to do it all next time we do the Big Breaking Change.

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This change is 

[nical]

r? @kvark

Note that I put default::Vector4D in lieu of default::HomogeneousVector because I prefer it that way but that's up for debate. The rest should be fairly uncontroversial I think.

[emilio]

Servo benefits from these annotations don't they? Plus must_use is stable now, so maybe we should just remove the cfg_attr.

[nical]

Ah nice! I hadn't realized it was stable in function annotations now. I don't know whether servo uses the unstable feature.
I'll remove the cfg_attr.

[kvark]

Reviewed 8 of 8 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @nical)

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src/lib.rs, line 143 at r1 (raw file):

    use super::*;

    pub type Point2D<T> = TypedPoint2D<T, UnknownUnit>;

if we end up with just Point2D<T, U = UnknownUnit>, what would be the use for default module?

[nical]

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src/lib.rs, line 143 at r1 (raw file):

Previously, kvark (Dzmitry Malyshau) wrote…

if we end up with just Point2D<T, U = UnknownUnit>, what would be the use for default module?

These default type parameters have never ended up being useful. I'm not even sure in what situations the compiler decides to make usre of that information.

[nical]

@bors-servo r=kvark

[bors-servo]

📌 Commit 65c0e85 has been approved by kvark

[bors-servo]

⌛ Testing commit 65c0e85 with merge b37eb9d...

[bors-servo]

☀️ Test successful - checks-travis
Approved by: kvark
Pushing b37eb9d to master...