Code cleanup of \bigl related stuff:

Code cleanup of \bigl related stuff:
	* src/cursor.C
	(LCursor::plainInsert): Move special \bigl stuff from here to
	MathNestInset::interpret
	(LCursor::macroModeClose): try to intepret the current macro before
	it is simply inserted

	* src/mathed/math_nestinset.C
	(MathNestInset::doDispatch): try to intepret the argument of
	LFUN_SELFINSERT also if it is longer than one character

	* src/mathed/math_nestinset.[Ch]
	(MathNestInset::interpret): new, moved from LCursor::plainInsert

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@13786 a592a061-630c-0410-9148-cb99ea01b6c8