ctf: allow declaration scopes to check if the declaration is overlapping

Needed for expanding aliases

Change-Id: I97039e706002602347cb6d06fbcfecbbd084b55d
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>

Author: MatthewKhouzam

ctf/org.eclipse.tracecompass.ctf.core/src/org/eclipse/tracecompass/ctf/core/event/metadata/DeclarationScope.java

@@ -197,7 +197,8 @@ public void registerType(String name, IDeclaration declaration)
      */
     public void registerIdentifier(String name, IDeclaration declaration) throws ParseException {
         /* Check if the type has been defined in the current scope */
-        if (fIdentifiers.containsKey(name)) {
+        IDeclaration iDeclaration = fIdentifiers.get(declaration);
+        if (iDeclaration != null && !Objects.equals(iDeclaration, declaration)) {
             throw new ParseException("Identifier has already been defined:" + name); //$NON-NLS-1$
         }