[acpica] Set alignment on acpi_table_facs to appease Clang

The acpi_table_facs, like many other ACPI structs, uses byte-packing to
match ACPI specification, but that means Clang insists on generating a
call to __atomic_compare_exchange_n intrisic to satistfy alignment
requirements when trying to atomically set the value for GlobalLock.
This is undesirable, especially since acpi_table_facs does not need
one byte alignment. So to appease Clang, we explicitly set the 4 byte
alignment for this struct, and enable -Wpadded error for this struct to
ensure we catch any potential future regressions.

Change-Id: I638bd500ba01d5a6f38ccd598e66a6ba65460e84

[public][ulib][dev] Add __FALLTHROUGH macro for warning suppression

GCC 7 enables -Wimplicit-fallthrough with -Wextra, so we'll get it.
Clang has it available, so start using it and clean up code accordingly.

The GCC feature will actually recognize some formulaic comments to
suppress the warning. But there's also an explicit syntax, and
C++17 added a standard one. So use that instead, via the new macro
__FALLTHROUGH in <zircon/compiler.h>.

TC-36 #comment Clean up code in preparation for more -Wimplicit-fallthrough

Change-Id: I28309c91c32db1313d52f4255836c5ea687e141f

[prebuilt] Roll Clang toolchain

Clang now contains only statically built libc++ for host as a single
archive so we no longer to pass additional flags for statically linking
C++ library.

Change-Id: If00ce91b619f457bc5961a68aca5bffd789ee8c3

[prebuilt] Update Clang toolchain

This change also fixes errors caused by -Wnull-pointer-arithmetic.

Change-Id: Id4ee4e1c6308a03508061a5a3ebe2817ee05b109

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[zircon][mxtl->fbl] Rename mxtl to fbl

Change-Id: Ie21b6498e1bfb0a7fa0315e40b9e5c3ee78646be

[acpica] Make enabling debug features easier

With this, turning on the debug output is mostly just specifying
ENABLE_ACPI_DEBUG=1 while building. Docs coming soon for how to use the ACPICA
debug interfaces.

Change-Id: I14ccdeedad004e3d127861a6b2f2201e499026f4

[ulib][acpica] implement AcpiOsUnmapMemory

Fixes handle leak from devhost:acpi.

MG-1000 #done

Change-Id: Ibb5592dbb5231dc203c75d04b161b4cc06c84388

[acpica] convert osfuchsia.c to c++

Change-Id: I91bcc63a07b9ed35e4168af2de51795ee6ae5cf2

[acpi] Use more conservative CFLAGS

ACPICA and the ACPI service were building with -Wno-strict-aliasing,
which silences warnings about strict aliasing violations. This takes
the more conservative approach of disabling strict-aliasing-based
optimizations.

Change-Id: I42c4a4d4fd121a20ee19437ae31779ee6a011297

[build] flatten the build

Previously we treated kernel/, system/, and third_party/ as
overlays on a shared namespace. This required the concept
of "canonical" module names, and a lot of complexity to ensure
that things didn't collide and the build worked.

This change gets rid of that, no longer passes -I to make,
so that include directives from our *.mk files do not magically
wildcard across various paths, etc.

The most user-visible change is that everywhere where a module
name is specified (MODULE_DEPS, MODULE_LIBS, etc), full module
names like kernel/lib/io or system/ulib/mxio must be used instead
of previously-allowed "short" names like lib/io and ulib/mxio.

The build output still has a similar shape, but the first segment
of the module path (kernel/, system/, or third_party/) is no
longer elided under $(BUILDDIR)

Change-Id: I525aba1da1c86eb7a86007bddc669f7eeebfedd5

[build][musl] refer to musl libc as ulib/c

This makes the build rules and the intermediate
output files easier to understand, without having
to modify the path where musl libc lives.

The biggest observeable difference is the build
intermediate files:

$ ls build-magenta-pc-x86-64/ulib/c
config-module.h libc.abi.h libc.abi.stamp libc.so libc.so.id libc.so.strip
libc.a libc.abi.o libc.a.opts libc.so.abi libc.so.opts third_party

which previously were at build-magenta-pc-x86/ulib/musl
and named libmusl.*

and the replacing of ulib/musl with ulib/c in the library
dependencies of all the rules.mk files (the vast bulk of
this change)

Change-Id: If9c5d522099d2c9ac5bdb666b8e67a2eb3d316ee

[ulib][acpica] Fix Clang warnings

This code is compiled in two places, so both need the warning disabled.

Change-Id: I64bc172849b04e73edf27586db64401992b1db5e

[build] do not export libacpica.a and libruntime.a

Change-Id: I9c66416dc73180a2a8444dc25d76830918d339a0

[build] Use boolean flags to enable Clang

This is to match other flags used by the build.

Change-Id: Idd1c1714aff3d03dbc58b92a2cbe0ee0a75d8089

[acpica] Relocate acpica ulib to third_party/ulib

Change-Id: I6be8461a2246fcd55da37132a553ff6e2d17ef53