More fixes to access and buffer compilation.

test/bad_double_access.ink

@@ -0,0 +1,10 @@
+P :: struct {
+	v : float2;
+}
+
+vertex main :: () {
+	p : P;
+	p.v.x.y = 2.0;
+	// v : float2;
+	// v.x.y.z = 2.0;
+}