Change `Mac OS 8 or 9' to `Mac OS Classic'.

Change `Mac OS 8 or 9' to `Mac OS Classic'.
(Mac OS): Update feature support status.
(Mac Input): List supported input scripts.  Remove description
about `mac-keyboard-text-encoding'.  Mention mouse button
emulation and related variables.
(Mac International): Mention Central European and Cyrillic
support.  Now `keyboard-coding-system' is dynamically changed.
Add description about coding system for selection.  Add
description about language environment.
(Mac Environment Variables): Mention
`~/.MacOSX/environment.plist'.  Give example of command line
arguments.  Add Preferences support.
(Mac Directories): Explicitly state that this node is for Mac OS
Classic only.
(Mac Font Specs): Mention specification for scalable fonts.  List
supported charsets.  Add preferred way of creating fontsets.  Add
description about `mac-allow-anti-aliasing'.
(Mac Functions): Add descriptions about `mac-set-file-creator',
`mac-get-file-creator', `mac-set-file-type', `mac-get-file-type',
and `mac-get-preference'.