container groundwork / splitting welded weapons (trunk only)

container groundwork / splitting welded weapons (trunk only)

      Some miscellaneous changes preparatory to enhancing the container
interface.  This also fixes a minor inconsistency in object manipulation:
askchain() wouldn't let you split a stack of welded weapons but getobj()
would, so you couldn't get rid of part of the stack using 'D' or #loot,
but you could with 'd' (and post-3.4.3, with #adjust).  Now getobj() will
behave like askchain(); if you have 3 cursed daggers welded to your hand,
you won't be able to drop 1 or 2 of them anymore.