The small ascii art in InsetMathCancel::draw has line continuation characters at
eol, this make consecutive lines be andled as one. The use of a block comment
instead of single line comments makes this less of a "problem." Also it removes
a warning with gcc 4.7.
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@40699 a592a061-630c-0410-9148-cb99ea01b6c8
