[x86] Run clang-format

This converts a bunch of the old LK style to the newer style.

Change-Id: I0f9dfc6b2b9b30b7630dc1e2271e8da815edd1d8

[kernel][x86] Implement startup-time code patching for SMAP instructions

Add a macro, APPLY_CODE_PATCH_FUNC(), which allocates some placeholder
instructions and declares how to replace them with working code on
kernel startup.

The initial use case is filling out the STAC and CLAC instructions
conditionally depending on whether the CPU supports SMAP.

The mechanism is a little more general than this initial use case
requires. My intention is the mechanism will be usable for inline
assembly that can get inlined into multiple places.

Change-Id: I213504db574f58c2d093d2648771c03048775c09

[kernel][status][arch] Use zx_status_t throughout kernel/arch

Change-Id: I051aaaee84c6e7776b0054171f8d69320d812fcb

[kernel][vm] move vm.h to the new spot and remove some unused code

Change-Id: I69f1b804fb95dd44e3e0619943e8809519aa82ca

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[kernel][x86] Add a global variable to cache x86_feature_test(X86_FEATURE_SMAP)

This simplifies the check in _x86_copy_to_or_from_user(). The
assembly code can access the global rather than having to take
smap_avail as an argument.

This is more of a cleanup than a performance improvement. Though
x86_feature_test() isn't trivial, it doesn't appear to add noticeable
overhead to the context switch.

Change-Id: I93529a0093366a212ae9214ac0e0ffc886ff1595

[kernel][x86][user_copy] De-duplicate _x86_copy_from_user/_x86_copy_to_user()

Now that these two functions no longer do an address range check, they
are identical and can be de-duplicated. (The low-level copying code
is identical on x86, unlike AArch64.)

Change-Id: I24860b665843805288f64145f17dfaca3504516a

[kernel][x86][user_copy] Move is_user_address_range() checks to C++ code

There's no need to call from C++ to assembly back to C++ to do the
is_user_address_range() checks. We can just do the checks in C++ in
the first place.

This roughly matches what is done in the ARM64 case.

Change-Id: Id3ef5722b91c660cdb8f4a5d0293c7899088ec84

[kernel][x86] conversion of x86 arch code to cpp

Minimum amount of work to convert the code to
keep the structure similar.

Change-Id: Id7e65014ba30ec32d8249889a22b62fbe959874f

[kernel][x86] brute force rename arch/x86/* files from .c to .cpp

Change-Id: I8ec0a28f71a7d4d3eba4f022873e59dbbbd0bd1e