wined3d: Always handle WINED3DSPR_INPUT registers as input registers in shader_get_registers_used().

The "attributes" vertexshader field is now derived from the input signature,
and only used to speed up matching D3D9 vertex declaration elements to shader
inputs. D3D8 and D3D10 both explicitly specify input registers.

The original implementation treated the string target in IHlink as a
separate entity from the moniker target.  In reality, the string target 
is just the moniker target's display name and setting one reference also
sets the other.

jscript: Make sure retv pointer is initialised in exec_source even if no value needs to be returned.