vbox: import vbox_CAPI_v4_3.h from SDK

vbox_CAPI_v4_3.h is almost same as
sdk/bindings/xpcom/include/VBoxCAPI_v4_3.h of
http://download.virtualbox.org/virtualbox/4.3.2/VirtualBoxSDK-4.3.2-90405.zip,
but modified to fix preprocessor indentations by using cppi.
Signed-off-by: NRyota Ozaki <ozaki.ryota@gmail.com>