https://github.com/prusa3d/Slic3r/issues/443
Change of the PlaceholderParser:
All vector configuration values stored into the PlaceholderParser
are expected to be addressed by the extruder ID, therefore
if a vector configuration value is addressed without an index,
a current extruder ID is used.
Also a small fix of fan handling: The fan speed is set to zero
at the start of the G-code if the cooling for the initial extruder
is disabled.