Deflate

* Added `-t` (test) option to `libdeflate-gunzip`.

* Unaligned access optimizations are now enabled on WebAssembly builds.

* Fixed a build error when building with the Intel C Compiler (ICC).

* Fixed a build error when building with uClibc.

* libdeflate's CI system has switched from Travis CI to GitHub Actions.

* Made some improvements to test scripts.

* Added support for compression level 0, "no compression".

* Added an ARM CRC32 instruction accelerated implementation of CRC32.

* Added support for linking the programs to the shared library version of
libdeflate rather than to the static library version.

* Made the compression level affect the minimum input size at which compression
is attempted.

* Fixed undefined behavior in x86 Adler32 implementation. (No miscompilations
were observed in practice.)

* Fixed undefined behavior in x86 CPU feature code. (No miscompilations were
observed in practice.)

* Fixed installing shared lib symlink on macOS.

* Documented third-party bindings.

* Made a lot of improvements to the testing scripts and the CI configuration
file.

* Lots of other small improvements and cleanups.

* Prevented gcc 10 from miscompiling libdeflate (workaround for
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94994).

* Removed workaround for gcc 5 and earlier producing slow code on ARM32. If
this affects you, please upgrade your compiler.

* New API function: `libdeflate_zlib_decompress_ex()`. It provides the actual
size of the stream that was decompressed, like the gzip and DEFLATE
equivalents.

* `libdeflate_zlib_decompress()` now accepts trailing bytes after the end of the
stream, like the gzip and DEFLATE equivalents.

* Added support for custom memory allocators. (New API function:
`libdeflate_set_memory_allocator()`)

* Added support for building the library in freestanding mode.

* Building libdeflate no longer requires `CPPFLAGS=-Icommon`.

* Fixed up stdcall support on 32-bit Windows: the functions are now exported
using both suffixed and non-suffixed names, and fixed `libdeflate.h` to be
MSVC-compatible again.

* The 32-bit Windows build of libdeflate now uses the "stdcall" calling
convention instead of "cdecl". If you're calling `libdeflate.dll` directly
from C or C++, you'll need to recompile your code. If you're calling it from
another language, or calling it indirectly using `LoadLibrary()`, you'll need
to update your code to use the stdcall calling convention.

* The Makefile now supports building libdeflate as a shared
library (`.dylib`) on macOS.

* Fixed a bug where support for certain optimizations and optional features
(file access hints and more precise timestamps) was incorrectly omitted when
libdeflate was compiled with `-Werror`.

* Added `make check` target to the Makefile.

* Added CI configuration files.

* `make install` now supports customizing the directories into which binaries,
headers, and libraries are installed.

* `make install` now installs into `/usr/local` by default. To change it, use
e.g. `make install PREFIX=/usr`.

* `make install` now works on more platforms.

* The Makefile now supports overriding the optimization flags.

* The compression functions now correctly handle an output data buffer >= 4 GiB
in size, and `gzip` and `gunzip` now correctly handle multi-gigabyte files (if
enough memory is available).