tame: Ignore duplicate conjunctive predicates in value list optimization error

This can occur in generated code (e.g. from proguic if a question-based
predicate inherits a predicate already specified).  This commit does not
change anything that's emitted; it merely allows proceeding.

TAMER can be smarter about this; I don't want to invest more time into
generalizing deduplication of predicates.

RELEASES.md

@@ -14,6 +14,16 @@ commits that introduce the changes.  To make a new release, run
 `tools/mkrelease`, which will handle updating the heading for you.
 
 
+NEXT
+====
+Compiler
+--------
+- Do not report value list optimization error on duplicate conjunctive
+  predicates.
+  - This doesn't emit code any differently, it merely permits the situation,
+    which can occur in generated code.
+
+
 v18.0.2 (2021-07-15)
 ====================
 This is a bugfix release that corrects issues with the Summary Page compiler

src/current/compiler/js.xsl

@@ -1030,7 +1030,8 @@
               not( c:eq )
               or (
                 c:eq/c:value-of
-                and $symtable-map( c:eq/c:value-of/@name )/@dim != '0' ) ] )" />
+                and $symtable-map( c:eq/c:value-of/@name )/@dim != '0' ) ] )
+      and count( distinct-values( $matches/c:eq/c:value-of/@name ) ) > 1" />
 </function>