P1979R0 Resolution to US086

Also fixes NB US 086 (C++20 CD)

Author: jensmaurer

source/modules.tex

@@ -495,11 +495,12 @@
 exported \grammarterm{module-import-declaration}{s}
 in $T$; such translation units are
 said to be \defnx{exported}{module!exported} by $T$.
-When a \grammarterm{module-import-declaration} in a module unit imports
-another module unit of the same module, it also imports
-all translation units imported by
-all \grammarterm{module-import-declaration}{s}
-in that module unit.
+Additionally, when a \grammarterm{module-import-declaration}
+in a module unit of some module $M$ imports another module unit $U$ of $M$,
+it also imports all translation units imported by
+non-exported \grammarterm{module-import-declaration}{s}
+in the module unit purview of $U$.\footnote{This is consistent
+with the rules for visibility of imported names\iref{basic.scope.namespace}.}
 These rules may in turn lead to the importation of yet more
 translation units.