- avoids false sharing

it is derived from crossbeam-utils, the main difference is that
this version provides a constant initialization routine

# __sys_realloc, __sys_free and __sys_malloc
- Add Errors section to docs
- Check if parameters are valid and warn/return error

# __sys_realloc, __sys_free
- Mark as unsafe
- Add detailed Safety section

# uhyve::get_application_parameters()
- make internal block unsafe and add Todos and Fixmes since this still needs some work!

* Fix some typos

* Fix linter warning: Function returns () instead of !

* Replace assert!(x == y) with assert_eq!(x,y)

Since we aren't downloading from cargo.io cargo download isn't actually needed in this workflow.

- use suggestions of the Rust documentation

because the branch "devel" isn't longer supported

- instead of the x86 crate

* Refactor: Fix Clippy warnings

- Added support for empty println!()
- use short hand initialization when possible
- replace if x==false with if !x
- replace unwrap_or(function_call()) with unwrap_or_else(|| function_call())
- and others

* Update to Rust edition 2018
 - Mostly just adds crate::

scheduler::init has nothing to do and can be removed

Replace volatile_write with standardized version of this intrinsic

Replace volatile_load with standardized version of this intrinsic

Refactor this method to make it clearer that this currently depends on uhyve.
Other hypervisors will not provide the BOOT_INFO.
This change should also make the function safe to use.

- requires PR rust-lang/rust#71839
- consequently, the latest nightly compiler has to be used

* CI: Reformat steps with 2 spaces as indent
  Previously some indents had 3 spaces
* CI: Add Qemu demo tests on libhermit-rs commits
* Test if libhermit-rs can run the demo defined in rusty-hermit. This currently only works for ubuntu
* CI: Add Qemu Test on Windows and MacOS
* CI: Add timeout for qemu smp steps
  Something is going wrong on macos and windows with qemu and smp
* CI: Run CI for all pushes

The previous implementation isn't deadlock free.
The current implementation based on a paper form Andrew Birrel.
It is not efficient and must be revised.

If the Environment variable HERMIT_LOG_LEVEL_FILTER is set at compile time to a string matching the Name of a Levelfilter enum value, then that value is used for the Levelfilter.
If the Environment variable is not set, or the name doesn't match, then LevelFilter::Info is used by default, which is the same as it was before.

- remove typos
- simplify CondQueue handling

This commits adds testing of libhermit-rs for pushes and PRs. Both debug and release builds are tested with 1 and 2 cores each.

Tests are done via the rusty-hermit demo in rusty-hermit. rusty-hermit is cloned and checked out to the devel branch. The demo is then compiled with the version of libhermit-rs that triggered the build and not the version specified as a submodule in rusty-hermit.

rusty-hermit including libhermit-rs is compiled fresh every time, but cargo dependencies such as uhyve and cargo-download are cached to speed up build time.

* improve the hypervisor detection
* prefer the results from uhyve because cupid returns sometimes wrong results

Cleanup of PCI Device initialization:
- handle both IOSpace and 32/64-bit Memory BARs
- add generic function to mm: map(), which maps a physical buffer to a
   newly allocated virtual address range
- add function to memory map the PCI memory bars, warn on multifunction devices
- check pci device header-type to ensure we don't read/write garbage
- remove sys_pci_find_adapter, since it is not used anywhere