Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Use string literals in string descriptors for marginally
better readability.

Submitted by: Christoph Mallon

Provide one global language string descriptor for
american english instead of giving each module its
own.

Submitted by: Christoph Mallon

Modify the FreeBSD USB kernel code so that it can be compiled directly
into the FreeBSD boot loader, typically for non-USB aware BIOSes, EFI systems
or embedded platforms. This is also useful for out of the system compilation
of the FreeBSD USB stack for various purposes. The USB kernel files can
now optionally include a global header file which should include all needed
definitions required to compile the FreeBSD USB stack. When the global USB
header file is included, no other USB header files will be included by
default.

Add new file containing the USB stack configuration for the
FreeBSD loader build.

Replace some __FBSDID()'s by /* $FreeBSD$ */ comments. Now all
USB files follow the same style.

Use cases:
- console in loader via USB
- loading kernel via USB

Discussed with: Hiroki Sato, hrs @ EuroBSDCon

Correct some bInterval USB template descriptor values.

MFC after: 3 days

- Add some comments about the origin of some USB descriptors.

MFC after: 7 days

- Add more USB templates for various USB device classes
- Add basic template support for USB 3.0
- Export definition of template sysctl numbers through usb_ioctl.h

MFC after: 7 days