When the scope is not found on ancestors, create on current scope.

This solves comment https://github.com/cc65/cc65/pull/1358#issuecomment-3193961949

doc/ca65.sgml

@@ -1320,7 +1320,7 @@ if you want to access the "other" symbol <tt/bar/, you would have to write:
 </verb></tscreen>
 
 The above example also shows that to search a scope that is not yet defined in
-the code above the usage, you must use the namespace token (<tt/::/) and
+the code above the usage, you should use the namespace token (<tt/::/) and
 specify the full scope name, to allow the assembler to create the scope at the
 correct place.
 

src/ca65/symbol.c

@@ -94,10 +94,14 @@ SymTable* ParseScopedIdent (StrBuf* Name, StrBuf* FullName)
         */
         Scope = SymFindAnyScope (CurrentScope, Name);
         if (Scope == 0) {
-            /* Scope not found */
-            SB_Terminate (FullName);
-            Error ("No such scope: `%m%p'", FullName);
-            return 0;
+            /* Scope not found, create a new scope here */
+            Scope = SymFindScope (CurrentScope, Name, SYM_ALLOC_NEW);
+            if (Scope == 0) {
+                SB_Terminate (FullName);
+                /* Scope not found */
+                Error ("Can't create scope: `%m%p'", FullName);
+                return 0;
+            }
         }
 
     } else {