wined3d: Only store the palette index in the alpha component when the primary render target uses P8.

This was already done in other places but I missed this spot.

Binding's implementation uses the same names, what makes reading logs
harder.

server: Initialise the apc_call_t union in async_set_result to all zero to avoid a Valgrind warning.

rpcss: Zero the memory of several variables before writing them to the pipe to silence Valgrind warnings.

glScalef(1.0, -1.0, 1.0) does the same as the glMultMatrix with the
invymat matrix, and it is more optimal.