Misc. documentation and source comment typo fixes

Found via `codespell -q 3 -L uint,od,objext,ba,cmo,bae,ans,struc,fo,clos,goin,upto,thru`
Revert changes in previous commit

Examples/ruby/exceptproxy/example.i

@@ -14,7 +14,7 @@
 %}
 
 
-/* The EmpytError doesn't appear in a throw declaration, and hence
+/* The EmptyError doesn't appear in a throw declaration, and hence
   we need to tell SWIG that the dequeue method throws it.  This can
   now be done via the %catchs feature. */
 %catches(FullError) *::enqueue;