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/meta/movable.h

@@ -15,7 +15,7 @@
 
 // Helper to decide if an object of type T is "movable", i.e. if it can be
 // copied to another memory location using memmove() or realloc() C functions.
-// C++ only gurantees that POD types (including primitive types) are
+// C++ only guarantees that POD types (including primitive types) are
 // movable.
 template<typename T>
 struct wxIsMovable