new warning in 2.2.x branch

[Uwe Stöhr]

Compiling today's branch I get:

RowPainter.cpp
D:\LyXGit\2.2.x\src\RowPainter.cpp(698): warning C4244: 'argument': 
conversion from 'double' to 'int', possible loss of data 
[D:\LyXGit\2.2.x\compile-2015\src\LyX.vcxproj]

JMarc, this slipped in form a commit from you to master. Could you 
please have look?

thanks and regards
Uwe