[basic.def.odr] Rephrase sentence to avoid double-negative

Author: jensmaurer

source/basic.tex

@@ -421,10 +421,11 @@
   of an overload set\iref{basic.lookup,over.match,over.over}
   in an overload resolution performed
   as part of forming that expression or conversion,
-  unless it is a pure virtual function and either
-  the expression is not an \grammarterm{id-expression} naming the function with
-  an explicitly qualified name or
-  the expression forms a pointer to member\iref{expr.unary.op}.
+  and either
+  it is not a pure virtual function or
+  the expression is an \grammarterm{id-expression} naming the function with
+  an explicitly qualified name
+  that does not form a pointer to member\iref{expr.unary.op}.
   \begin{note}
 This covers
   taking the address of functions\iref{conv.func,expr.unary.op},