Remove unused headers from hsStlUtils.h (and push them downstream where needed)

Also fix a couple of plString and header issues identified by Paradox on GCC/Clang

Sources/Plasma/FeatureLib/pfPython/cyAccountManagement.h

@@ -50,6 +50,7 @@ You can contact Cyan Worlds, Inc. by email legal@cyan.com
 //
 
 #include <vector>
+#include <string>
 
 typedef struct _object PyObject;
 typedef struct PyMethodDef PyMethodDef;

Sources/Plasma/FeatureLib/pfPython/plPythonSDLModifier.h

@@ -46,7 +46,7 @@ class plPythonFileMod;
 class plStateDataRecord;
 class plSimpleStateVariable;
 
-#include "hsStlUtils.h"
+#include <map>
 #include "plModifier/plSDLModifier.h"
 
 #include "pyGlueHelpers.h"

Sources/Plasma/FeatureLib/pfPython/pySDL.h

@@ -49,7 +49,8 @@ You can contact Cyan Worlds, Inc. by email legal@cyan.com
 //////////////////////////////////////////////////////////////////////
 
 #include "HeadSpin.h"
-#include "hsStlUtils.h"
+#include <vector>
+
 #include "pyGlueHelpers.h"
 
 class plStateDataRecord;