Improve compile time (or at least don't regress it)

[Boddlnagg]

We can use this issue to track the current compile time (and memory usage) by posting the output of cargo rustc --features all -- -Z time-passes. Also don't forget to include rustc -V.

[Boddlnagg]

Here are some numbers (for 2e914f7) (without the time required to compile dependencies) showing the effect of rust-lang/rust#36524 between rustc 1.13.0-nightly (c772948b6 2016-09-20) and rustc 1.13.0-nightly (4f9812a59 2016-09-21):

	time [secs]	rlib size [bytes]
Before (Debug)	351.46	263.572.720
Before (Release)	506.68	154.972.432
After (Debug)	285.87	187.843.258
After (Release)	305.48	119.689.216

See details in a gist.

[Boddlnagg]

I added the #[inline] attribute to more functions in df557dd and measured again, this time comparing rustc 1.13.0-nightly (4f9812a59 2016-09-21) and rustc 1.13.0-nightly (d0623cf7b 2016-09-26)

	time [secs]	rlib size [bytes]
Before (Debug)	250.86	99.626.880
Before (Release)	259.66	97.387.268
After (Debug)	223.87	76.829.116
After (Release)	221.5	74.582.690

Adding more #[inline] improved everything but the item-bodies checking phase, and the latest compiler changes improved compile times further!

I have updated the gist to include the latest measurements.

[Boddlnagg]

I just did a new test run (with PR #48), and observed that the compile times slightly decreased, but the memory usage and output rlib size increased quite a bit (as always, see the gist for details):

	time [secs]	rlib size [bytes]	max memory [MB]
2016-09-26 (Debug)	223.87	76.829.116	2396
2016-09-26 (Release)	221.5	74.582.690	2384
2017-12-20 (Debug)	214.25	117.216.458	4334
2017-12-20 (Release)	215.84	114.618.966	4325

This can have many reasons, because both rustc and winrt itself changed between those two measurements. Maybe worth investigating, but I don't have time for that.