Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Set the pin to output on attach, we can't assume it already is.

Reviewed by: gonzo

Fix legal staff in GPIO sources:
- license clause now contains "AUTHOR AND CONTRIBUTORS"
instead of just "AUTHOR"
- Add license/copyright to gpioc.c

Spotted by: Edward Tomasz Napierala, Andrew Turner

Initial GPIO bus support. Includes:
- GPIO bus controller interface
- GPIO bus interface
- Implementation of GPIO led(4) compatible device
- Implementation of iic(4) bus over GPIO (author: Luiz Otavio O Souza)

Tested by: Luiz Otavio O Souza, Alexandr Rybalko