Typo in size recalculation of HBox.

[Adam Malinowski]

Function

void HBox::draw

starts with a line

_RecalculateSizes(a.h, &Drawable::GetMinimalWidth);

It's incorrect; should be:

_RecalculateSizes(a.w, &Drawable::GetMinimalWidth);

[Adam Malinowski (adayah)]

Note: this bug had not been discovered before, because we had only used VBox in our test program.