[virtcon] Don't set window size for invalid FD

The invalid value for vc->fd is -1 rather than 0.

Change-Id: Ib3e4e9ca6b4b56680438596d474084f457666a1f

[virtcon] Fix virtcon status bar flashing

It takes vc-input multiple calls to vc_write to finish updating the
status bar. Wait until all the calls are made before redrawing the
status bar.

Change-Id: I37ba541d4ee43139a0881030926e40a489d90191

[virtcon] Add support for hotplugging

This change adds support for hotplugging to the virtcon. If multiple
displays are connected, the virtcon will use the display which was
attached first. The virtcon's contents and scrollback are kept when
switching between displays, although long lines will be truncated if
the virtcon moves to a smaller display.

When no display is connected, the console continues to function
normally, except without rendering anything. All checks for whether or
not any gfx operations should be done are in vc-device.

Change-Id: I467b9b1792f4d43803b521ec564dfe1873b85a97

[system][core] add more console ctrl keys

This allows to switch to the zircon console via
alternate keys.

win key: switch display (vc or gpu)
vol up: previous console
vol down: next console

Very useful in the case USB is down or GPU is
down:

1- if usb is down you can switch to the kernel log
2- if gpu is down you can't switch

Change-Id: I733c6da2d997596ecf2d6ce8d420be533570a5ef

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[devmgr][virtcon] display netsvc output on vc1 in netboot mode

- virtcon can now execute a specific command in vc1 if one is
provided via the --run option
- virtcon uses a white-on-blue color scheme for this
- devmgr provides --run dlog ... when starting netsvc in netboot
mode

Change-Id: I7008db178aa25a8f3dc549a7af46d790d11c6472

[virtcon] Use the new MX_OK and MX_ERR_* mx_status_t names

Change-Id: I89dd39bd11d4d4b89321424cfc910b605688e307

[virtcon] cleanup

- remove some unused header includes
- remove unused vcdebug.h (xprintf was not used and now virtcon
filters its own debug prints out of the debug log console so
printf is safe to use if needed)
- clean up rules.mk to better reflect shared sources, libraries
- move shared code from main.cpp to vc-input.cpp
- no longer include main.cpp in virtual-console-test
- remove global lock, no longer needed in new single threaded design

Change-Id: I5aacc0f95f817f25ce96bbfa2f74d4877e9c4a16