enlightment for protection and magic cancellation (trunk only)

The bug report about losing/regaining the Protection intrinsic reminded
me of a couple of things.  First, as an intrinsic, Protection seems to be
completely useless and we ought to redo it.  Second, periodically people in
the newsgroup have complained about how it's nearly impossible to figure
out the important--possibly crucial--armor attribute of magic cancellation.
Wearing a cloak greatly increases characters' survival rates, but beyond
that, magic cancellation is just spoiler fodder.

     This doesn't do much about Protection other than to change "you are
protected" into "you have a <small,moderate,&c> defense bonus" similar to
how the attributes conferred by rings of increase damage and increase
accuracy are handled.  For magic cancellation, it adds new feedback:
  You are protected.  -- mc factor 3
  You are guarded.    -- mc factor 2
  You are warded.     -- mc factor 1
(with no extra feedback for mc factor 0, the normal naked state.  The mc 3
case might cause some confusion over the changed meaning of a previously
existing item, but I think it'll be ok and not need re-wording.)

doc/fixes35.0

@@ -207,6 +207,7 @@ digging can activate or disarm some types of traps
 some monsters can eat tins in addition to corpses to cure some ailments
 add Roderick Schertler's pickup_thrown patch
 add ability to sort the list when viewing known spells with '+' command
+describe magic cancellation from worn armor in enlightment/end-of-game feedback
 
 
 Platform- and/or Interface-Specific New Features