WiimoteReal: Add a hidapi IO implementation

Based on ca0c2efe7ab19c85449d52dd1bf4beec8603bbfe. Credits go to flacs.
However, unlike the original commit, hidapi does not completely replace
the current implementations, so we can still connect Wiimotes with 1+2
(without pairing).

Also, it is only used on Linux and OS X for now. This removes the
advantage of having only one implementation but there is no other
choice: using hidapi on Windows is currently impossible because
hid_write() is implemented in a way that won't work with Wiimotes.

Additionally:
* We now check for the device name in addition to the PID/VID so we can
  support the Balance Board and maybe third-party Wiimotes too. This
  doesn't achieve anything with the DolphinBar but it does with hidraw.
* Added a check to not connect to the same device more than once.

CMakeLists.txt

@@ -835,6 +835,33 @@ else()
 endif()
 list(APPEND LIBS ${ICONV_LIBRARIES})
 
+if(NOT ANDROID)
+	include(FindHIDAPI OPTIONAL)
+	find_package(HIDAPI)
+	if(HIDAPI_FOUND)
+		message("Using shared ${HIDAPI_LIBRARIES} ${HIDAPI_VERSION}")
+		include_directories(${HIDAPI_INCLUDE_DIRS})
+		list(APPEND LIBS ${HIDAPI_LIBRARIES})
+	else()
+		include_directories(Externals/hidapi/hidapi)
+		if(APPLE)
+			message("Using static hidapi from Externals")
+			add_subdirectory(Externals/hidapi/mac)
+			list(APPEND LIBS hidapi)
+		elseif(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+			message("Using static hidapi-hidraw from Externals")
+			add_subdirectory(Externals/hidapi/linux)
+			list(APPEND LIBS hidapi-hidraw udev)
+		else()
+			message("Using static hidapi-libusb from Externals")
+			add_subdirectory(Externals/hidapi/libusb)
+			list(APPEND LIBS hidapi-libusb)
+		endif()
+	endif()
+	set(HIDAPI_FOUND 1)
+	add_definitions(-DHAVE_HIDAPI=1)
+endif()
+
 find_library(OPENSLES_LIBRARIES NAMES OpenSLES)
 find_path(OPENSLES_INCLUDE_DIR NAMES SLES/OpenSLES.h)