Add <span> tag and limited support for CSS styles to wxHTML.

Parse "style" attributes of the HTML tags and honour those of them that can be
mapped to the HTML 3 attributes.

Also add a handler for <span> tag.

Closes #10631.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64443 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/html/htmltag.h

@@ -108,6 +108,8 @@ public:
 
         Returns @true on success and @false if @a par is not colour specification or
         if the tag has no such parameter.
+
+        @see ParseAsColour()
     */
     bool GetParamAsColour(const wxString& par, wxColour* clr) const;
 
@@ -148,6 +150,21 @@ public:
     */
     bool HasParam(const wxString& par) const;
 
+    /**
+        Parses the given string as an HTML colour.
+
+        This function recognizes the standard named HTML 4 colours as well as
+        the usual RGB syntax.
+
+        @since 2.9.1
+
+        @see wxColour::Set()
+
+        @return @true if the string was successfully parsed and @a clr was
+            filled with the result or @false otherwise.
+     */
+    static bool ParseAsColour(const wxString& str, wxColour *clr);
+
     //@{
     /**
         This method scans the given parameter. Usage is exactly the same as sscanf's