Version 1.5.3

Unfortunately, when fixing a freeze in Version 1.3.3 I only fixed that bug on the 1.3.x branch, but forgot to fix it on the trunk. So 1.5.3 fixes the same bug again: when switching to engineering mode with the number 0 on the stack, the calculator would freeze (enter a busy loop).
Additionally, 1.5.3 won't crash anymore when YaRPNcalc is started while in Landscape mode (on devices that support it).