* faq-api.xml: Add FAQ entry "Why do some of my old symlinks don't
work anymore?"
* new-features.sgml: Fix symlink text. Add new UTF-16 symlinks.
* overview2.sgml: Add text about new UTF-16 symlinks and potential
problems with old symlinks.
* pathnames.sgml: Fix typo.
* setup2.sgml: Extend text about problems with symlinks.
* cygwinenv.sgml: Fix codepage:utf8 text in terms of setting
environment variables.
* new-features.sgml: New file describing new Cygwin 1.7 features.
Layout is preliminiary only.
* overview.sgml: Insert content of new-features.sgml.