Fix crash when assigning to bool class fields (#95)

With `Type.bool`, size is 1, so dividing by 8 isn't the right way to convert to byteSize. Instead, we need to use the `byteSize` property that does the proper ceiling division.

tests/compiler/class-with-boolean-field.ts

@@ -0,0 +1,9 @@
+class A {
+  boolValue: bool;
+}
+
+export function test(): bool {
+  let a: A;
+  a.boolValue = true;
+  return a.boolValue;
+}