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/newobject1_runme.rb

@@ -8,7 +8,7 @@
 #
 # Ruby's GC is somewhat broken in that it will mark some more stack space
 # leading to the collection of local objects to be delayed.
-# Thus, upon invokation, it sometimes you can wait up to several
+# Thus, upon invocation, it sometimes you can wait up to several
 # instructions to kick in.
 # See: http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/7449
 #

Examples/test-suite/ruby/newobject2_runme.rb

@@ -2,7 +2,7 @@
 #
 # Ruby's GC is somewhat broken in that it will mark some more stack space
 # leading to the collection of local objects to be delayed.
-# Thus, upon invokation, it sometimes you can wait up to several
+# Thus, upon invocation, it sometimes you can wait up to several
 # instructions to kick in.
 # See: http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/7449
 #

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