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/html/helpdata.h

@@ -203,7 +203,7 @@ protected:
     wxHtmlBookRecArray m_bookRecords;
 
     wxHtmlHelpDataItems m_contents; // list of all available books and pages
-    wxHtmlHelpDataItems m_index; // list of index itesm
+    wxHtmlHelpDataItems m_index; // list of index items
 
 protected:
     // Imports .hhp files (MS HTML Help Workshop)

include/wx/html/htmlfilt.h

@@ -45,7 +45,7 @@ public:
 //--------------------------------------------------------------------------------
 // wxHtmlFilterPlainText
 //                  This filter is used as default filter if no other can
-//                  be used (= uknown type of file). It is used by
+//                  be used (= unknown type of file). It is used by
 //                  wxHtmlWindow itself.
 //--------------------------------------------------------------------------------
 

include/wx/html/htmlpars.h

@@ -163,7 +163,7 @@ protected:
     // Adds tag and proceeds it. Parse() may (and usually is) called from this method.
     // This is called from Parse() and may be overridden.
     // Default behaviour is that it looks for proper handler in m_Handlers. The tag is
-    // ignored if no hander is found.
+    // ignored if no handler is found.
     // Derived class is *responsible* for filling in m_Handlers table.
     virtual void AddTag(const wxHtmlTag& tag);
 
@@ -236,7 +236,7 @@ public:
     //   is capable of handling italic, bold, font and paragraph tags
     virtual wxString GetSupportedTags() = 0;
 
-    // This is hadling core method. It does all the Steps 1-3.
+    // This is handling core method. It does all the Steps 1-3.
     // To process step 2, you can call ParseInner()
     // returned value : true if it called ParseInner(),
     //                  false etherwise
@@ -282,7 +282,7 @@ public:
     // (with respect to output encoding)
     wxString Parse(const wxString& input) const;
 
-    // Returns character for given entity or 0 if the enity is unknown
+    // Returns character for given entity or 0 if the entity is unknown
     wxChar GetEntityChar(const wxString& entity) const;
 
     // Returns character that represents given Unicode code

include/wx/html/htmlwin.h

@@ -260,7 +260,7 @@ public:
 
     // Set HTML page and display it. !! source is HTML document itself,
     // it is NOT address/filename of HTML document. If you want to
-    // specify document location, use LoadPage() istead
+    // specify document location, use LoadPage() instead
     // Return value : false if an error occurred, true otherwise
     virtual bool SetPage(const wxString& source);
 
@@ -503,8 +503,8 @@ protected:
     bool m_makingSelection;
 
 #if wxUSE_CLIPBOARD
-    // time of the last doubleclick event, used to detect tripleclicks
-    // (tripleclicks are used to select whole line):
+    // time of the last double-click event, used to detect triple clicks
+    // (triple clicks are used to select whole line):
     wxMilliClock_t m_lastDoubleClick;
 
     // helper class to automatically scroll the window if the user is selecting

include/wx/html/winpars.h

@@ -249,7 +249,7 @@ private:
 
 //-----------------------------------------------------------------------------
 // wxHtmlWinTagHandler
-//                  This is basicly wxHtmlTagHandler except
+//                  This is basically wxHtmlTagHandler except
 //                  it is extended with protected member m_Parser pointing to
 //                  the wxHtmlWinParser object
 //-----------------------------------------------------------------------------