minor H98 anomaly: class declarations

[Ross Paterson]

4.3.1 has

   topdecl     -> class [scontext =>] simpleclass [where cdecls]
   scontext    -> simpleclass
               |  ( simpleclass[1] , ... , simpleclass[n] )      (n>=0) 
   simpleclass -> qtycls tyvar

implying that the class being declared can be qualified:

	class Foo.C a where ...

in contrast to every other kind of declaration.  Nor does the text
explain what this could mean.  Shouldn't the first line be

   topdecl     -> class [scontext =>] tycls tyvar [where cdecls]

(GHC doesn't allow qualification; Hugs and Nhc allow it and do strange things.)