Merge branch 'doc-for-mfleming' of git://github.com/geneC/syslinux into elflink

Merge branch 'doc-for-mfleming' of git://github.com/geneC/syslinux into elflink

Pull txt/ and doc/ updates from Gene Cumm,

* 'doc-for-mfleming' of git://github.com/geneC/syslinux:
  txt/syslinux.txt: rewrap long command
  txt/Makefile: add isolinux.txt, pxelinux.txt
  txt/: Add isolinux.txt, pxelinux.txt
  txt/syslinux-cli.txt: Version on Ctrl-N
  txt/Makefile: order-only prerequisite
  txt/: Add common file for derivatives
  txt/syslinux.cfg.txt: Updates
  txt/syslinux.txt: synopsis, extlinux.sys, wrap long command
  txt/syslinux-cli.txt: Path rules
  txt/syslinux.cfg.txt: Add SENDCOOKIES, example config
  txt/syslinux.cfg.txt: Add SYSAPPEND
  doc/syslinux.txt: grammar
  Fix SERIAL directive in docs