FreeBSD support for usb-connected devices in adb

FreeBSD (and other systems as well) may use libusb to work with USB devices.
libusb is integrated in FreeBSD base system in recent builds (8.0+),
however in other systems it may need include libusb.h like <libusb/libusb.h>
and install library from devel/libusb port or other repository.

Submitted change not supports events (attach/detach) as libusb 1.0 lacks
such functionality and in order to make code more portable I've not used
workarounds as in earlier changeset.

Code was tested on FreeBSD 8.0-RC1, HTC Hero (1.0.0.A6288, Android 1.5)
diff --git a/adb/Android.mk b/adb/Android.mk
index f3eaa6e..6325e53 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -25,6 +25,12 @@
   LOCAL_LDLIBS += -lpthread -framework CoreFoundation -framework IOKit -framework Carbon
 endif
 
+ifeq ($(HOST_OS),freebsd)
+  USB_SRCS := usb_libusb.c
+  EXTRA_SRCS := get_my_path_freebsd.c
+  LOCAL_LDLIBS += -lpthread -lusb
+endif
+
 ifeq ($(HOST_OS),windows)
   USB_SRCS := usb_windows.c
   EXTRA_SRCS := get_my_path_windows.c