Cycles Hair: Fixed hair shape and inclusion of multiple attributes for triangle primitives

When using triangle primitives this fix enables 'closed tip'. 

UVs and vertex colours are added when using triangle primitives for hair.

Two new preset modes have also been included to allow easy access to curves and triangle planes.

intern/cycles/render/curves.h

@@ -33,9 +33,11 @@ void curvebounds(float *lower, float *upper, float3 *p, int dim);
 
 typedef enum curve_presets {
 	CURVE_CUSTOM,
+	CURVE_FAST_PLANES,
 	CURVE_TANGENT_SHADING,
 	CURVE_TRUE_NORMAL,
-	CURVE_ACCURATE_PRESET
+	CURVE_ACCURATE_PRESET,
+	CURVE_SMOOTH_CURVES
 } curve_presets;
 
 typedef enum curve_primitives {