Make the function ZSTD_compressSequencesAndLiterals() available in kernel
space. This will be used by Intel QAT driver.

Additionally, (1) expose the function ZSTD_CCtx_setParameter(), which is
required to set parameters before calling ZSTD_compressSequencesAndLiterals(),
(2) update the build process to include `compress/zstd_preSplit.o` and
(3) replace `asm/unaligned.h` with `linux/unaligned.h`.

Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>

Test the kernel build with the standard warnings enabled so that we
don't miss issues like fixed in PR #2802.

Stacked on top of PR #2802 so CI passes, so it includes the fix. But, I
won't merge until it is merged, so @solbjorn gets the credit for the
fix.

Fix the `unaligned.h` shim in the tests that was causing corruption in
the tests. Note that this is a problem with the test shim, not the
kernel code.