The new kfreebsd-kernel-headers version 0.44 is based on kFreeBSD 8.0. This new kernel version introduce a new USB stack with a totally different API. This breaks the build of at least freeglut, libsdl1.2, hal and qemu, but probably a lot more. While the long term solution is to add support for the new API, this is something that will take time. We should find to try a solution as soon as possible, as it starts to block package migration to testing.
Does for libsdl1-2 help including of more headers and http://www.freebsd.org/cgi/cvsweb.cgi/ports/devel/sdl12/files/patch-src_joystick_bsd_SDL_sysjoystick.c ? Having 8.0 as a default should bring us usb stack compatible with libusb-1.0.
From http://libusb.org/wiki/Libusb1.0:
libusb-1.0 includes a platform abstraction layer allowing for cross-platform compatibility. Linux and Darwin (Mac OS X) are supported in the latest release.
FreeBSD 8 includes a FreeBSD-specific reimplementation of the libusb-1.0 API, so your applications will probably work there too. The source code for this library can be found here.
Petr