Escape symbols when adding to library

Can't escape by default because the allowed characters differ in the
read-only libraries and existing schematics that reference them.  So,
escape when we import into standard KiCad Libraries

Fixes https://gitlab.com/kicad/code/kicad/issues/9419

eeschema/symbol_editor/symbol_editor_import_export.cpp

@@ -91,7 +91,9 @@ void SYMBOL_EDIT_FRAME::ImportSymbol()
     wxString symbolName = symbols[0];
     LIB_SYMBOL* entry = pi->LoadSymbol( fn.GetFullPath(), symbolName );
 
-    if( m_libMgr->SymbolExists( symbols[0], libName ) )
+    entry->SetName( EscapeString( entry->GetName(), CTX_LIBID ) );
+
+    if( m_libMgr->SymbolExists( entry->GetName(), libName ) )
     {
         msg.Printf( _( "Symbol %s already exists in library '%s'." ), symbolName, libName );
 
@@ -105,7 +107,7 @@ void SYMBOL_EDIT_FRAME::ImportSymbol()
 
     m_libMgr->UpdateSymbol( entry, libName );
     SyncLibraries( false );
-    LoadSymbol( symbolName, libName, 1 );
+    LoadSymbol( entry->GetName(), libName, 1 );
 }