(byte-compile-not-obsolete-vars): Rename from byte-compile-not-obsolete-var.

(byte-compile-not-obsolete-vars): Rename from byte-compile-not-obsolete-var.
It's a list now.
(byte-compile-not-obsolete-funcs): New variable.
(byte-compile-warn-obsolete): Don't warn about functions if they are in
byte-compile-not-obsolete-funcs.
(byte-compile-variable-ref, byte-compile-defvar): Update for
byte-compile-not-obsolete-vars name-change and list nature.
(byte-compile-maybe-guarded): Suppress warnings about obsolete functions
and variables behind (f)boundp tests.