Rollup of 4 pull requests

[Centril]

Successful merges:

• Future-proof the Futures API #59119 (Future-proof the Futures API)
• Unsized rvalues: implement boxed closure impls. (2nd try) #59500 (Unsized rvalues: implement boxed closure impls. (2nd try))
• SGX target: Use linker option to avoid code CGU assignment kludge #59624 (SGX target: Use linker option to avoid code CGU assignment kludge)
• Remove invalid assertion back::link::from add_upstream_rust_crates(). #59696 (Remove invalid assertion back::link::from add_upstream_rust_crates().)

Failed merges:

r? @ghost

[Centril]

@bors r+ p=4

[bors]

📌 Commit 5a93250 has been approved by Centril

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:00fd75e6:start=1554484533056697214,finish=1554484619062687760,duration=86005990546
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---
[00:04:31]    Compiling panic_unwind v0.0.0 (/checkout/src/libpanic_unwind)
[00:04:33] error: hidden lifetime parameters in types are deprecated
[00:04:33]    --> src/libstd/panic.rs:326:44
[00:04:33]     |
[00:04:33] 326 |     fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
[00:04:33] 
[00:04:35] error: aborting due to previous error
[00:04:35] 
[00:04:35] error: Could not compile `std`.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)