make the std::map dumper work with keys that already have a const

qualification like 'const char *'

src/plugins/debugger/gdbengine.cpp

@@ -3022,8 +3022,13 @@ void GdbEngine::runCustomDumper(const WatchData & data0, bool dumpChildren)
     } else if (outertype == "std::map") {
         // We don't want the comparator and the allocator confuse gdb.
         // But we need the offset of the second item in the value pair.
-        extraArgs[2] = "(size_t)&(('std::pair<const " + inners.at(0)
-            + "," + inners.at(1) + ">'*)0)->second";
+        // We read the type of the pair from the allocator argument because
+        // that gets the constness "right" (in the sense that gdb can
+        // read it back;
+        QString pairType = inners.at(3);
+        // remove 'std::allocator<...>':
+        pairType = pairType.mid(15, pairType.size() - 15 - 2);
+        extraArgs[2] = "(size_t)&(('" + pairType + "'*)0)->second";
         extraArgs[3] = "0";
     } else if (outertype == "std::basic_string") {
         //qDebug() << "EXTRACT TEMPLATE: " << outertype << inners;