Make it possible to uses non-ascii labelstring, endlabelstring and

Make it possible to uses non-ascii labelstring, endlabelstring and
labelstring_appendix in layout files

	* src/text2.C
	(LyXText::setLayout): Translate labelwidthstring for paragraph
	(LyXText::getStringToIndex): labelwidthstring is now a docstring

	* src/buffer.[Ch]
	(Buffer::translateLabel): New method for translating a label if it
	is not already translated by the user in the layout file

	* src/lyxtext.h
	(setParagraph): labelwidthstring is now a docstring

	* src/support/lstrings.[Ch]
	(bool isAscii): New utility function: Determine whether a docstring
	contains only pure ascii

	* src/text3.C
	(LyXText::dispatch): setParagraph() now takes a docstring

	* src/lyxlayout.C
	(LyXLayout::read): Don't use from_ascii when reading labelstring_,
	endlabelstring_ and labelstring_appendix_

	* src/buffer_funcs.C
	(setLabel): labelwidthstring is now a docstring
	(setLabel): Use Buffer::translateLabel instead of Buffer::B_ to
	translate labels
	(expandLabel): ditto

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15855 a592a061-630c-0410-9148-cb99ea01b6c8