doc/misc/gnus.texi (HTML): Fix xref to EWW
Uniquify the 'size' symbol.

* frame.c (Qsize):
* w32notify.c (Qsize): Remove.
* lisp.h (Qsize): New decl.
* lread.c (Qsize): Now extern.
* w32notify.c (syms_of_w32notify): No need to defsym.