Avoid problems if the floor was already removed together with a wall.
5 lines of code changed in:
Merged bug fix from trunk: when building a new floor on top of an old floor,
the old one was never removed, resulting in a stack of floors in some buildable
areas.
13 lines of code changed in:
Backported from trunk: fix for bug #2028541: Any object using a non-default
move_slow_penalty was always saved with the value 0 because the code was
using FAST_SAVE_LONG instead of FAST_SAVE_DOUBLE for a floating-point value.
7 lines of code changed in: