The PAL can now advertise that it supports aligned allocation. If it
does not, then the memory provider will do the alignment for it.
This change still leaves the PAL responsible for systematic testing, but
it should now be much easier to lift that out.
It appears that clang-format 6 (which CI uses) removes a newline that
clang-format 7 doesn't, but will also not add. The new formatting
should keep 6 and 7 both happy.
This does not deallocate memory until the OS tells us that we are short
on memory, then tries to decommit all of the cached chunks (except for
the first page, used for the linked lists).
Nowhere near enough testing to commit to master yet!
The newer API (Windows 10 and newer) allows the allocator to ask for
strongly aligned memory.
This is enabled only if the `WINVER` macro is set to target Windows 10
or newer. There is now a CMake option to target older versions of
Windows, so we can test both code paths.
The Azure Pipelines config now includes a test of the compatibility
version. This runs only the release build, because it's mainly there as
a sanity check - 99% of the code is the same as the default Windows
config.
Move slow_allocator into a separate header in the snmalloc namespace and
rename it for consistency with the rest of the codebase. Delete its
copy and move constructors / assignment operators.
