Misc. typo and whitespace fixes

Found via `codespell -q 3 -L "uint,bae,objext,cmo,goin,struc,ois,upto"`
whitespaces were unintentionally fixed due to my editors settings.

Rebased patch #1327

Examples/test-suite/ruby/swig_assert.rb

@@ -21,7 +21,7 @@ end
 
 def swig_assert_simple(a)
   unless a
-    raise SwigRubyError.new("assertion falied.")
+    raise SwigRubyError.new("assertion failed.")
   end
 end