Fix spelling in comments and documentation using codespell

Apply the utility from https://github.com/codespell-project/codespell/
to fix spelling issues in the headers under both include and interface
directories and add a file with a couple of exceptions.

The exact command line used was:

    $ codespell -w -I misc/scripts/codespell.ignore -i 3 in*

include/wx/generic/dcpsg.h

@@ -90,7 +90,7 @@ public:
 
     void PsPrint( const wxString& psdata );
 
-    // Overrridden for wxPrinterDC Impl
+    // Overridden for wxPrinterDC Impl
 
     virtual int GetResolution() const wxOVERRIDE;
     virtual wxRect GetPaperRect() const wxOVERRIDE;

include/wx/generic/grid.h

@@ -302,7 +302,7 @@ public:
     // version only checks that the event has no modifiers. The derived
     // classes are supposed to do "if ( base::IsAcceptedKey() && ... )" in
     // their IsAcceptedKey() implementation, although, of course, it is not a
-    // mandatory requirment.
+    // mandatory requirement.
     //
     // NB: if the key is F2 (special), editing will always start and this
     //     method will not be called at all (but StartingKey() will)

include/wx/generic/grideditors.h

@@ -210,7 +210,7 @@ public:
         { return new wxGridCellFloatEditor(m_width, m_precision); }
 
     // parameters string format is "width[,precision[,format]]"
-    // format to choose beween f|e|g|E|G (f is used by default)
+    // format to choose between f|e|g|E|G (f is used by default)
     virtual void SetParameters(const wxString& params) wxOVERRIDE;
 
 protected:

include/wx/generic/private/grid.h

@@ -140,7 +140,7 @@ private:
     int m_col;
 };
 
-// header control retreiving column information from the grid
+// header control retrieving column information from the grid
 class wxGridHeaderCtrl : public wxHeaderCtrl
 {
 public:

include/wx/generic/progdlgg.h

@@ -120,7 +120,7 @@ protected:
     // called to disable the other windows while this dialog is shown
     void DisableOtherWindows();
 
-    // must be called to reenable the other windows temporarily disabled while
+    // must be called to re-enable the other windows temporarily disabled while
     // the dialog was shown
     void ReenableOtherWindows();