[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[unittest] Use ASSERT_NE()/EXPECT_NE() instead of ASSERT_NEQ()/EXPECT_NEQ()

This is to make the interface more consistent with gtest, which uses
the _NE suffix rather than _NEQ for "not equal".

Change-Id: Ic03fda7322ab79cbd806c8f849b6956d201c6d45

[utest][handles] don't treat handles as signed

Otherwise we can't build when they become unsigned.

Change-Id: I9af3e25c9716a41985320016c5559c09d6c8e520

[utest][core] MX_ERR_-ify the core unit tests

Change-Id: Iebfbeba437831ad4b85d1b0bc6d6dc22bb721de9

[magenta][sysgen] Make scalar OUTs returns instead

Change syscalls.sysgen to move scalar OUT params to the returns
list, instead of input args.

This clarifies the expectations of these parameters and allows us
to change the user-space signatures to more idiomatic
representations for any language.

It also makes the register-passing changes a little simpler.

Change-Id: Ia6f5f3e55516c85bb879d9e91af224ce26f0015f

[syscalls] update callers to mx_handle_wait_*() and deprecate

Change-Id: I7b0516007b99d58aee906eac62358625100ee32e

[signals] Remove legacy signal names

Change-Id: I6d4543358a16d16b9b9028ede06af40a632ba31b

[syscalls] update mx_handle_wait_one()

Change-Id: I03c03b0c02041e680e44930e4d8c22f380d26916

[utest][channel] msgpipe => channel in core utests

Change-Id: I6c50e0828fd905adaa75296952ae9caefaf88925

[magenta][syscalls] migrate all syscalls to the new names

If DEPCRECATE_COMPAT_SYSCALLS is defined, flag the compatibility
wrappers with the deprecated attribute.

Enable this in the Magenta build only for now.

Change-Id: I422b1294d9db2e56551eca65dede0e5d83f8b363

[system] align license and license banners with Fuchsia

This adjusts the Magenta userspace code to match the prevailing
license in Fuchsia (three-clause BSD), using the same banner
and license text.

Change-Id: I6b6d79435c5dbaa32027888874849e4f47aaa7be

[utest] Support categories

This will produce single binary from mxr tests and also seperate binary
for each test

Change-Id: I9345fbeab5751dda356cfd47a766c09957211923