Fix warnings detected by clang.

src/common/bspf.hxx

@@ -25,6 +25,7 @@
   @author Bradford W. Mott and Stephen Anthony
 */
 
+#include <climits>
 #include <cstdint>
 // Types for 8/16/32/64-bit signed and unsigned integers
 using Int8   = int8_t;

src/emucore/KidVid.cxx

@@ -25,8 +25,8 @@ KidVid::KidVid(Jack jack, const Event& event, const System& system,
                const string& rommd5)
   : Controller(jack, event, system, Controller::KidVid),
     myEnabled(myJack == Right),
-    mySampleFile(nullptr),
-    mySharedSampleFile(nullptr),
+//     mySampleFile(nullptr),
+//     mySharedSampleFile(nullptr),
     myFileOpened(false),
     myTapeBusy(false),
     myFilePointer(0),

src/emucore/KidVid.hxx

@@ -83,7 +83,7 @@ class KidVid : public Controller
     bool myEnabled;
 
     // The file handles for the WAV files
-    FILE *mySampleFile, *mySharedSampleFile;
+    // FILE *mySampleFile, *mySharedSampleFile;
 
     // Indicates if sample files have been successfully opened
     bool myFileOpened;

src/emucore/PointingDevice.cxx

@@ -15,8 +15,6 @@
 // this file, and for a DISCLAIMER OF ALL WARRANTIES.
 //============================================================================
 
-#include <climits>
-
 #include "Control.hxx"
 #include "Event.hxx"
 #include "System.hxx"

src/gui/GlobalPropsDialog.cxx

@@ -132,7 +132,6 @@ GlobalPropsDialog::GlobalPropsDialog(GuiObject* boss, const GUI::Font& font)
 int GlobalPropsDialog::addHoldWidgets(const GUI::Font& font, int x, int y,
                                       WidgetArray& wid)
 {
-  const int fontHeight = font.getFontHeight();
   int xpos = x, ypos = y;
   const int VGAP = 4;