Fix bug 3410 by Georg and me

Fix bug 3410 by Georg and me

	* src/support/tempname.C
	(tempName): Return FileName in utf8 encoding.

	* src/lyxsocket.[Ch]
	(LyXServerSocket::LyXServerSocket): Use FileName instead of string
	and set the env var LYXSOCKET in the filesystem encoding as this
	is what the client expects.

	* src/support/socktools.[Ch]
	(socktools::listen): Convert to FileName and use the filesystem
	encoding for the file names stored in the sockaddr_un struct.

	* src/client/client.C
	(socktools::connect): Convert to FileName and use the filesystem
	encoding for the file names stored in the sockaddr_un struct.
	(LyXDataSocket::LyXDataSocket, main): Convert to FileName.

	* src/lyx_main.C
	(LyX::exec): Use FileName instead of string in socket code.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@17749 a592a061-630c-0410-9148-cb99ea01b6c8