Print debug/version level instead of __anonymous in error messages.

When integer debug/version levels are used, ident is not defined,
causing Dsymbol::toChars() to print "__anonymous", which is unhelpful.
Instead, it should return the debug/version level being set as an
integer.

src/version.c

@@ -40,6 +40,18 @@ DebugSymbol::DebugSymbol(Loc loc, unsigned level)
     this->loc = loc;
 }
 
+char *DebugSymbol::toChars()
+{
+    if (ident)
+        return ident->toChars();
+    else
+    {
+        OutBuffer buf;
+        buf.printf("%d", level);
+        return buf.extractString();
+    }
+}
+
 Dsymbol *DebugSymbol::syntaxCopy(Dsymbol *s)
 {
     assert(!s);
@@ -117,6 +129,18 @@ VersionSymbol::VersionSymbol(Loc loc, unsigned level)
     this->loc = loc;
 }
 
+char *VersionSymbol::toChars()
+{
+    if (ident)
+        return ident->toChars();
+    else
+    {
+        OutBuffer buf;
+        buf.printf("%d", level);
+        return buf.extractString();
+    }
+}
+
 Dsymbol *VersionSymbol::syntaxCopy(Dsymbol *s)
 {
     assert(!s);

src/version.h

@@ -27,6 +27,7 @@ class DebugSymbol : public Dsymbol
     DebugSymbol(Loc loc, unsigned level);
     Dsymbol *syntaxCopy(Dsymbol *);
 
+    char *toChars();
     int addMember(Scope *sc, ScopeDsymbol *sds, int memnum);
     void semantic(Scope *sc);
     const char *kind();
@@ -42,6 +43,7 @@ class VersionSymbol : public Dsymbol
     VersionSymbol(Loc loc, unsigned level);
     Dsymbol *syntaxCopy(Dsymbol *);
 
+    char *toChars();
     int addMember(Scope *sc, ScopeDsymbol *sds, int memnum);
     void semantic(Scope *sc);
     const char *kind();

test/fail_compilation/test13786.d

@@ -1,9 +1,9 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/test13786.d(14): Error: debug __anonymous level declaration must be at module level
+fail_compilation/test13786.d(14): Error: debug 123 level declaration must be at module level
 fail_compilation/test13786.d(15): Error: debug abc declaration must be at module level
-fail_compilation/test13786.d(16): Error: version __anonymous level declaration must be at module level
+fail_compilation/test13786.d(16): Error: version 123 level declaration must be at module level
 fail_compilation/test13786.d(17): Error: version abc declaration must be at module level
 fail_compilation/test13786.d(20): Error: template instance test13786.T!() error instantiating
 ---