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*

interface/wx/bitmap.h

@@ -445,7 +445,7 @@ public:
         @param height
             The height of the bitmap in pixels, must be strictly positive.
         @param dc
-            DC from wich the scaling factor is inherited
+            DC from which the scaling factor is inherited
 
         @return @true if the creation was successful.