A few more minor fixes geared towards lgtm.com alerts (#6127)

* Remove unfilled formatting placeholders in KLT parser.
* Fix presumably unintentionally missing reference on PlanatPtr and ChunkyPtr call operators.
* Fix catching pointer and make use-after-free of workimg easier to spot.
Make sure all of our thrown exceptions derive from std::exception and then catch
by reference instead of by pointer.
* Fix mismatch between array form new and non-array form delete.
* Simplify memory management of embedded color profiles by unifying allocation to use operator new.

rtengine/lcp.cc

@@ -196,7 +196,7 @@ rtengine::LCPProfile::LCPProfile(const Glib::ustring& fname) :
     XML_Parser parser = XML_ParserCreate(nullptr);
 
     if (!parser) {
-        throw "Couldn't allocate memory for XML parser";
+        throw std::runtime_error("Couldn't allocate memory for XML parser");
     }
 
     XML_SetElementHandler(parser, XmlStartHandler, XmlEndHandler);
@@ -216,7 +216,7 @@ rtengine::LCPProfile::LCPProfile(const Glib::ustring& fname) :
 
             if (XML_Parse(parser, buf, bytesRead, done) == XML_STATUS_ERROR) {
                 XML_ParserFree(parser);
-                throw "Invalid XML in LCP file";
+                throw std::runtime_error("Invalid XML in LCP file");
             }
         } while (!done);