`ApplyShadow` result discarded during shader creation

[ajtribick]

The result of the ApplyShadow call here isn't used.

Celestia/src/celengine/shadermanager.cpp

Lines 2467 to 2469 in b54fa98

	if (props.hasShadowMap() && i == 0)
	ApplyShadow(false);
	}

Need to check what this does and either append the code to source or remove the call.

[375gnu]

oh, source += was lost when ApplyShadow was added to avoid code duplication.