Remove compiler warnings '-Wextra-semi' (see also PR #266)

I compiled with `-Wextra-semi -Werror=extra-semi` on Linux and Windows
(cross-compiled on Linux) and removed all "extra semicolon" warnings
I could find. I didn't check on macOS (yet).

Note: Linux configured with and w/o Pango but not w/o Xft. Compilation
with other options (e.g. Cairo) might still emit such warnings.

FL/Fl_Device.H

@@ -73,19 +73,19 @@ protected:
   /** Constructor that sets the graphics driver to use for the created surface. */
   Fl_Surface_Device(Fl_Graphics_Driver *graphics_driver) {pGraphicsDriver = graphics_driver; }
   /** Sets the graphics driver of this drawing surface. */
-  inline void driver(Fl_Graphics_Driver *graphics_driver) {pGraphicsDriver = graphics_driver;};
+  inline void driver(Fl_Graphics_Driver *graphics_driver) {pGraphicsDriver = graphics_driver;}
 public:
   virtual void set_current(void);
   virtual bool is_current();
   /** \brief Returns the graphics driver of this drawing surface. */
-  inline Fl_Graphics_Driver *driver() {return pGraphicsDriver; };
+  inline Fl_Graphics_Driver *driver() {return pGraphicsDriver; }
   /** The current drawing surface.
    In other words, the Fl_Surface_Device object that currently receives all graphics requests.
    \note It's possible to transiently remove the GUI scaling factor in place in the current
    drawing surface with \ref fl_override_scale(). */
   static inline Fl_Surface_Device *surface() {
     return surface_ ? surface_ : default_surface();
-  };
+  }
   /** \brief The destructor. */
   virtual ~Fl_Surface_Device();
   static void push_current(Fl_Surface_Device *new_current);

FL/Fl_File_Browser.H

@@ -55,9 +55,9 @@ public:
   ~Fl_File_Browser();
 
   /**    Sets or gets the size of the icons. The default size is 20 pixels.  */
-  uchar         iconsize() const { return (iconsize_); };
+  uchar         iconsize() const { return (iconsize_); }
   /**    Sets or gets the size of the icons. The default size is 20 pixels.  */
-  void          iconsize(uchar s) { iconsize_ = s; redraw(); };
+  void          iconsize(uchar s) { iconsize_ = s; redraw(); }
 
   /**
     Sets or gets the filename filter. The pattern matching uses
@@ -70,10 +70,10 @@ public:
     the fl_filename_match()
     function in FLTK.
   */
-  const char    *filter() const { return (pattern_); };
+  const char    *filter() const { return (pattern_); }
   int           load(const char *directory, Fl_File_Sort_F *sort = fl_numericsort);
-  Fl_Fontsize  textsize() const { return Fl_Browser::textsize(); };
-  void          textsize(Fl_Fontsize s) { Fl_Browser::textsize(s); iconsize_ = (uchar)(3 * s / 2); };
+  Fl_Fontsize  textsize() const { return Fl_Browser::textsize(); }
+  void          textsize(Fl_Fontsize s) { Fl_Browser::textsize(s); iconsize_ = (uchar)(3 * s / 2); }
 
   /**
     Sets or gets the file browser type, FILES or
@@ -81,14 +81,14 @@ public:
     files and directories are shown. Otherwise only directories are
     shown.
   */
-  int           filetype() const { return (filetype_); };
+  int           filetype() const { return (filetype_); }
   /**
     Sets or gets the file browser type, FILES or
     DIRECTORIES. When set to FILES, both
     files and directories are shown. Otherwise only directories are
     shown.
   */
-  void          filetype(int t) { filetype_ = t; };
+  void          filetype(int t) { filetype_ = t; }
   void errmsg(const char *emsg);
   /**
     Returns OS error messages, or NULL if none. Use when advised.

FL/Fl_File_Chooser.H

@@ -142,7 +142,7 @@ public:
   void ok_label(const char *l);
   const char * ok_label();
   void preview(int e);
-  int preview() const { return previewButton->value(); };
+  int preview() const { return previewButton->value(); }
 private:
   void showHidden(int e);
   void remove_hidden_files();

FL/Fl_Paged_Device.H

@@ -36,7 +36,7 @@
 class FL_EXPORT Fl_Paged_Device : public Fl_Widget_Surface {
 protected:
   /** \brief The constructor */
-  Fl_Paged_Device() : Fl_Widget_Surface(NULL) {};
+  Fl_Paged_Device() : Fl_Widget_Surface(NULL) {}
 public:
   /**
    Possible page formats.
@@ -99,7 +99,7 @@ public:
    */
   static const page_format page_formats[NO_PAGE_FORMATS];
   /** \brief The destructor */
-  virtual ~Fl_Paged_Device() {};
+  virtual ~Fl_Paged_Device() {}
   virtual int begin_job(int pagecount = 0, int *frompage = NULL, int *topage = NULL, char **perr_message = NULL);
   /** Synonym of begin_job(int pagecount, int *frompage, int *topage, char **perr_message).
    For API compatibility with FLTK 1.3.x */

FL/Fl_SVG_Image.H

@@ -162,7 +162,7 @@ public:
   virtual void color_average(Fl_Color c, float i);
   virtual void draw(int X, int Y, int W, int H, int cx = 0, int cy = 0);
   void draw(int X, int Y) { draw(X, Y, w(), h(), 0, 0); }
-  virtual Fl_SVG_Image *as_svg_image() { return this; };
+  virtual Fl_SVG_Image *as_svg_image() { return this; }
   virtual void normalize();
 };