Fix hyperref-soul conflict and sanitize hyperref management

Fix hyperref-soul conflict and sanitize hyperref management

* src/BufferParams.cpp:
	- always require hyperref if it's used.
	- only call PDFOptions::writeLaTeX if hyperref is required
	  (and not provided by textclass).
* src/PDFOptions.{cpp,h}:
	- (writeLaTeX): remove unneeded hyper_required argument
* src/LaTeXFeatures.cpp:
	- special definition for pdflatex ct markup when hyperref is used
	  (fix bug 4504).

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@22629 a592a061-630c-0410-9148-cb99ea01b6c8