Rename the driver hooks in the DRM to something a little more

    understandable: preinit -> load postinit -> (removed) presetup ->
    firstopen postsetup -> (removed) open_helper -> open prerelease ->
    preclose free_filp_priv -> postclose pretakedown -> lastclose
    postcleanup -> unload release -> reclaim_buffers_locked version ->
    (removed)
postinit and version were replaced with generic code in the Linux DRM
    (drivers now set their version numbers and description in the driver
    structure, like on BSD). postsetup wasn't used at all. Fixes the savage
    hooks for initializing and tearing down mappings at the right times.
    Testing involved at least starting X, running glxgears, killing
    glxgears, exiting X, and repeating.
Tested on: FreeBSD (g200, g400, r200, r128) Linux (r200, savage4)