Warnings due to x***arrow commit

[Richard Heck]

CXX InsetMathXArrow.o


../../src/mathed/InsetMathXArrow.cpp: In member function 'virtual void
lyx::InsetMathXArrow::mathmlize(lyx::MathStream&) const':

../../src/mathed/InsetMathXArrow.cpp:116:8: warning: 'arrow' may be used
uninitialized in this function [-Wmaybe-uninitialized]

<< arrow << cell(1) << cell(0)

^

../../src/mathed/InsetMathXArrow.cpp: In member function 'virtual void
lyx::InsetMathXArrow::htmlize(lyx::HtmlStream&) const':

../../src/mathed/InsetMathXArrow.cpp:157:43: warning: 'arrow' may be
used uninitialized in this function [-Wmaybe-uninitialized]

<< MTag("span", "class='xabottom'") << arrow << ETag("span")