Fix conversion of n-th roots to mathematica and octave syntax.

Fix conversion of n-th roots to mathematica and octave syntax.

	* src/mathed/MathExtern.C
	(pipeThroughOctave): take into account that the output from octave
	may contain ansi control sequences.

	* src/mathed/InsetMathRoot.[Ch]
	(InsetMathRoot::mathematica): new virtual method to output n-th
	roots in mathematica syntax.

	* src/mathed/InsetMathRoot.C
	(InsetMathRoot::octave): octave has not a root() command.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@16559 a592a061-630c-0410-9148-cb99ea01b6c8