Draft: backends/native: Work with old libdrm
commit a775241e recently introduced usage of a sort of new API, drmModeCloseFb. Unfortunately, this API has not yet made it into freedesktop-sdk.
As an interim answer, this commit adds a drmIoctl based reimplementation of drmModeCloseFb that only gets used if the real implementation isn't available in libdrm.
Later we can just drop this function without changing any other code.