[fdio] Use -fvisibility=hidden

This exports only the symbols declared in the public headers.

ZX-1895 #comment

Test: full system build
Change-Id: Idf762ea94518d668c26235047a5917bc4d4399ef

[fdio] Merge pipe() and socketpair() impls

As far as I can tell, there's no reason for these implementations to be
separate. Merging the two means we'll be able to recover the client type
of a zx::socket from the information in the kernel. Specifically, a
stream socket with no control plane will map to a pipe (aka socketpair).

Test: pipe and socketpair tests continue to pass
Change-Id: If0251b662daa1ad4ce4017c7d949016204c667a1

[fdio] Rename newsocket.c to socket.c

We've removed the old socket implementation. The "new" socket is no
longer new.

Test: No behavior change
Change-Id: Iea4e2c09c893cc0c5b955584eadb4f0ae56844a0

[fuchsia][process] Refer to a loader service handle by name

Test: no functional change
Change-Id: Ib2ad232a6e593c75e4968a98172dc3c55a0392b5

[fdio] return library to all C code

With the move to the C fidl bindings, the C++ custom bindings went
away and nothing in fidl.cpp needs C++ any more.

Reduces our library dependencies and keeps us consistent across
the fdio codebase.

Test: system boots, runtests passes
Change-Id: Ie5a4740f450b50178c928d82e4b588a2449a91aa

[fidl] Use autogenerated fuchsia-io header

Remove hand-rolled verison.

Test: CQ

ZX-1919 #comment In Progress

Change-Id: I8816a9616067e4d437385db4d552d385e33eb975

[fdio] Open sockets via FIDL

Use the fuchsia.net.LegacySocketProvider interface to open sockets on a
netstack. This feature is enabled when FIDL_SOCKET_PROVIDER=1.

US-505
Test: existing tests + manual testing with corresponding garnet change

Change-Id: I0a5833d5c94fe0438182f265b58ef7800941b001

[fidl] Rename FIDL directories

These names more closely match what we publish in the SDK. Ideally, we'd
use . as the separator, but Zircon's build system cannot handle . in
directory names, so we use - instead.

Test: Builds.
Change-Id: Ia420a364d2accac39faebade8f3f8ed72088556a

[fdio] Add fdio_spawn and fdio_spawn_etc

These functions provide a simple interface for spawning processes. The
interface is loosely modelled after posix_spawn and provides the most
commonly used functionally from liblaunchpad.so. Clients with more
sophisticated needs should use the process-launcher service directly.

Eventually, these functions will use the process-launcher service as a
backend. This CL contains just interface.

Change-Id: I9a8a9d542b5f79e56d8c82b00c226f79c5355e19

[fdio] Split libbootfs out of libfdio

There's no relationship between the code that processes bootfs data and
the rest of fdio. This CL moves the bootfs code into a separate (static)
library.

Change-Id: I3d129829d04f88a4ee0cecbe637548e1b0934733

[fido] Remove dispatcher

This functionality is unused.

Change-Id: Ib467a10854a079a0eb7da35328031e361aa6ed61

[netstack] Remove obsolete oldsocket code.

We've enabled the newsocket protocol by default. This removes the code
specific to oldsocket.

ZX-1134 #progress

Change-Id: I74f85a6afbacd4399a6f2b40fb3bcf8a03663472

[fdio] Re-enable newsocket for netstack protocol

This reverts commit 9a9c346d96b1c09da06b187537932256fd30e087.

I had reverted to oldsocket speculatively, to test if newsocket was the cause
of some test flakiness in chromium. It was not, so I'm unreverting.

Change-Id: Ib80aebec04850f0cb14564e7c1815fd8fa1d365d

[fdio] Revert to oldsocket temporarily.

This is an exploratory revert to see if the newsocket change was the
cause of a chromium test failure:
https://bugs.chromium.org/p/crashpad/issues/detail?id=219

Change-Id: I17cca90585a339b62a261d9bde126a449e0690b3

[rio][fidl] Convert RemoteIO operations to FIDL2

This patch updates all Zircon servers to respond to
either RIO or FIDL2 requests. This will allow
compatibility with clients speaking either protocol.

Although this patch allows clients and servers to communicate
with FIDL2 instead of RIO, it is a slight modification
from strict FIDL2 standards: Most servers don't implement
the exact FIDL2 Object / Node / File / Directory protocols,
they just implement a subset of all operations. Updating
these servers to exactly implement these interfaces
will occur in subsequent patches.

ZXRIO_FIDL toggle can be used to request RIO or FIDL2 client
requests.

TO-496 #done
ZX-1358 #comment In Progress

Change-Id: Ia52f469e553be977deb3d0f280ba3efaf36ed893

[fdio] add low level debugging facility

Debugging stdio from inside the guts of its implementation is not fun.

This adds an optional (disabled and uncompiled by default) low level
debug facilty for poking around inside libfdio when necessary.

Change-Id: If1c82b11c2fe2475be37a7848357fc4f3f300512

[netstack] Enable new socket protocol by default.

This enables the new socket protocol for FDIO.

ZX-1134 #progress

Change-Id: If13f24870f0eb601b95d3886f336ad594b0ffe49

[fdio][socket] remotesocket -> newsocket

Most of this code is identical, but new sockets only have a
single handle (the socket itself), and do not rely on remoteio
for control transfers (so we introduce zxsio_misc() and _ioctl(),
which are initially just stubs).

Change-Id: I5884cfbe7383d3137b51b56e250dd358514fff69

[fdio][socket] skeleton for new socket type

Set ENABLE_NEW_SOCKET to true to get the new path
(which as of this change does nothing).

Change-Id: Id358b49d8a8f0b4574128ae7cc9477dfdd92a829

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94