Xv reput changes v2

[ville.syrjala at nokia.com]

Second installment of Xv reput changes.

Patches 09-13 are new. Patch 14 was modified. The rest should be the
same as before.

ReputImage clipping should now match the behaviour of a regular
XPutImage or a non-overlay XvPutImage fairly closely.

The ReputImage hook was changed to pass all the src/dst coordinates
instead of just dst_x and dst_y. This isn't strictly necessary but
leaving it out would require duplicate bookkeeping in the driver.

A call to the ModeSet hook was added to xf86DisableUnusedFunctions().

I think this set is pretty much done now. I'll wait for review comments
before I'll touch it again.