Mana shield patch.

  This patch is ready to be aplied to a Vanilla angband 2.9.5-alpha wich
has been patched with the Mana curse patch.

  It adds a new item flag : TR3_MANA_SHIELD
replacing the (I hope) unnused flag : TR3_XXX2

  Objects to get this flag should get marked with MANA_SHIELD at
edit/object.txt

  When the player is wearing an item with this flag he will not die by
suffering damage above its hit points instead all damage above its hit
points will be deduced from his mana points. Only when damage exceeds
hip points plus mana points the player will die.
  If the player has both mana curse and mana shield, he will suffer
the mana curse and mana shield will be ignored.
  Which objects should get this very powerful shield is up to the
mantainer and users.

TO DO:
  The descriptions given about mana shield by self knowledge and *identify*
should be better (or more artistic).
  Wizard mode commands do not know about this flag.

Luthien
josedura@wanadoo.es