Fix bug 1395 by Stefan Schimanski:

Fix bug 1395 by Stefan Schimanski:

Locking counter added to MacroData: it is increased before drawing/
metric calculations and decreased afterwards in InsetMathMacro. If a
macro is already locked at that point, "Self reference: \foo" is
drawn instead of the macro definition to avoid endless loops.
Moreover inside of the arguments of the macro the counter is
temporarily decreased as those cases do not cause loops. (fixes bug
#1395)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@17836 a592a061-630c-0410-9148-cb99ea01b6c8