[PATCH 0/2] Improve renderproto gradients documentation

[Andrea Canciani]

Currently RENDER does not specify conditions on the number of stops
required for a valid gradients, but the X server returns an error
whenever the stops are less than 2.

In addition to this, some clients are currently misusing radial
gradients by requesting the rendering of "invalid" radial gradients
and the X server is not returning an error.

This patchset is an attempt to fix these issues in the protocol.

NB: pixman already supports both single-stop gradients and arbitrary
radial gradients.