d/dmd: Merge upstream dmd c185f9df1

Adds new virtual isVersionCondition, this is so that in the code
generation pass, a ConditionDeclaration's condition can be identified
without requiring a Visitor function.

Reviewed-on: https://github.com/dlang/dmd/pull/9591

From-SVN: r270300

gcc/d/dmd/MERGE

-d7ed327edb0b01ad56e7e73e77b3401cd565675e
+c185f9df1789456c7d88d047f2df23dd784f1182
 
 The first line of this file holds the git revision number of the last
 merge done from the dlang/dmd repository.

gcc/d/dmd/cond.h

@@ -39,6 +39,7 @@ public:
     virtual Condition *syntaxCopy() = 0;
     virtual int include(Scope *sc, ScopeDsymbol *sds) = 0;
     virtual DebugCondition *isDebugCondition() { return NULL; }
+    virtual VersionCondition *isVersionCondition() { return NULL; }
     virtual void accept(Visitor *v) { v->visit(this); }
 };
 
@@ -91,6 +92,7 @@ public:
     VersionCondition(Module *mod, unsigned level, Identifier *ident);
 
     int include(Scope *sc, ScopeDsymbol *sds);
+    VersionCondition *isVersionCondition() { return this; }
     void accept(Visitor *v) { v->visit(this); }
 };