Fix strange bibtex problem by converting some more functions to use FileName

Fix strange bibtex problem by converting some more functions to use FileName
instead of std::string

	* src/support/lyxlib.h
	* src/support/getcwd.C
	(getcwd): return a FileName, not a std::string in filesystem encoding

	* src/support/filetools.[Ch]
	(makeAbsPath): return a FileName, not a std::string in undefined encoding

	* src/support/lyxlib.h
	* src/support/tempName.C
	(makeAbsPath): return a FileName, not a std::string in undefined encoding

	* many other files: Adjust to the changes above

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@16399 a592a061-630c-0410-9148-cb99ea01b6c8