[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[mxio][musl] Add skeleton support for file-backed mmap

- Relocated mmap to unistd.c
- Added MXRIO_MMAP operation to remoteio
- Add support in mmap for file-backed, non-private file mappings.

Notably, the mmap operation is not yet supported by any filesystems,
so any non-anonymous calls to mmap will fail in the MXRIO operation.

Change-Id: I3e48a1bfcd35f2c4061262d9758d65e147c7538c

[ulib][musl] Reduce unnecessary exports

There are still lots of symbols in the export list that should not
really be part of the ABI. But this picks off some low-hanging fruit.

Change-Id: I86168858de89bd327fb70cd4ca639caa1e502702

[musl][pthreads] Remove more vestiges of robust mutex support in stdio

This special 0x40000000 value was used to mark robust mutexes to be
cleaned up (ie, waiters awoken) at pthread_exit time. We no longer
have such a mechanism, and so no longer need the linked list of file
locks.

Change-Id: Id38ecc1908ad8b62289c4796978639f12c3a759a

[musl] Remove legacy linux syscall mechanism entirely

Change-Id: Ia013bac87e87a7a4528b496ac26da649ad130da0

[musl][atomics] Use C11 atomics in public types

Change-Id: Ie684384c127d881fbeccb1290adce622d368d136

Revert "[musl][atomics] Use C11 atomics in public types"

This reverts commits f2373edae22bc921a41286318243b3985102b510 and
c97bbfb0755f81841769a12a12ba5fbe86144a6b

This breaks libc++ builds:

FAILED: src/CMakeFiles/unwind_objects.dir/libunwind.cpp.o
/b/swarm_slave/w/irzvTVgH/kitchen-workdir/buildtools/toolchain/clang+llvm-x86_64-linux/bin/clang++ -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libunwind/include -I/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include -stdlib=libc++ -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -fcolor-diagnostics -target x86_64-fuchsia --sysroot=/b/swarm_slave/w/irzvTVgH/kitchen-workdir/out/sysroot/x86_64-fuchsia -std=c++11 -g -Werror=return-type -W -Wall -Wchar-subscripts -Wconversion -Wmismatched-tags -Wmissing-braces -Wnewline-eof -Wno-unused-function -Wshadow -Wshorten-64-to-32 -Wsign-compare -Wsign-conversion -Wstrict-aliasing=2 -Wstrict-overflow=4 -Wunused-parameter -Wunused-variable -Wwrite-strings -Wundef -Wno-error -pedantic -D_DEBUG -D_LIBUNWIND_IS_NATIVE_ONLY -fPIC -fno-exceptions -funwind-tables -I/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include -stdlib=libc++ -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -fcolor-diagnostics -target x86_64-fuchsia --sysroot=/b/swarm_slave/w/irzvTVgH/kitchen-workdir/out/sysroot/x86_64-fuchsia -std=c++11 -fstrict-aliasing -fno-rtti -MD -MT src/CMakeFiles/unwind_objects.dir/libunwind.cpp.o -MF src/CMakeFiles/unwind_objects.dir/libunwind.cpp.o.d -o src/CMakeFiles/unwind_objects.dir/libunwind.cpp.o -c /b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libunwind/src/libunwind.cpp
In file included from /b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libunwind/src/libunwind.cpp:19:
In file included from /b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/algorithm:640:
In file included from /b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/memory:643:
/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/atomic:1713:17: error: address argument to atomic operation must be a pointer to _Atomic type ('volatile bool *' invalid)
{return __c11_atomic_exchange(&__a_, true, __m);}
^ ~~~~~
/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/atomic:1716:17: error: address argument to atomic operation must be a pointer to _Atomic type ('bool *' invalid)
{return __c11_atomic_exchange(&__a_, true, __m);}
^ ~~~~~
/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/atomic:1719:10: error: address argument to atomic operation must be a pointer to _Atomic type ('volatile bool *' invalid)
{__c11_atomic_store(&__a_, false, __m);}
^ ~~~~~
/b/swarm_slave/w/irzvTVgH/kitchen-workdir/third_party/llvm/runtimes/libcxx/include/atomic:1722:10: error: address argument to atomic operation must be a pointer to _Atomic type ('bool *' invalid)
{__c11_atomic_store(&__a_, false, __m);}

Change-Id: I2fba5de2b1abc16f6e2ab3ae11f4b6ee1e70f135

[musl][atomics] Use C11 atomics in public types

For now, use a shim around compare and swap. Followup patches will
rewrite them directly into the C11 style, but for now minimize noise.

Change-Id: Idf3626fea6318b8508d6e65f2634a71e93cf866c

[musl] Clang format musl

Change-Id: Iaa26e3e6fe4ebf11abd9b548c053c205f2d08af3

[musl] Use #pragma once in musl's internal headers

This only replaces existing ifdef guards in internal headers. It doesn't
add them to files that didn't have guards, or to public headers.

Change-Id: Ie012ac77ed95ff476291c7391230af086ad8a019

[musl] Clean up some warnings in musl's make build

Change-Id: Ib305f1d161634156fad8f7303208c49be66c855c

[musl] clang format musl

Change-Id: I3bc6ab7655410514691cd07f08454f3afd41d9b3

[magenta] Initial commit