Change type of member variables Fl_Graphics_Driver::ascent + descent

Type short is too small for Fl_Cairo_Graphics_Driver and font sizes ≥ 110.

FL/Fl_Graphics_Driver.H

@@ -383,7 +383,7 @@ public:
   Fl_Fontsize size; /**< font size */
   Fl_Font_Descriptor(const char* fontname, Fl_Fontsize size);
   virtual FL_EXPORT ~Fl_Font_Descriptor() {}
-  short ascent, descent;
+  int ascent, descent;
   unsigned int listbase;// base of display list, 0 = none
 };