new compiler warning in master

[Uwe Stöhr]

Compiling current git master I get

  InsetSpace.cpp
D:\LyXGit\Master\src\insets\InsetSeparator.cpp(213): warning C4244: 
'+=': conversion from 'double' to 'int', possible loss of data

This was introduced by commit
http://www.lyx.org/trac/changeset/d4ca8d74041094f623cc891a30b4dc537137431c/lyxgit 


Enrico, could you please have a look?

btw. do I have to document something new after your patch?

thanks and regards
Uwe