fix #H7659 - accessing freed memory by cutworm()

fix #H7659 - accessing freed memory by cutworm()

hmon() can destroy the weapon being used, and known_hitum() would
still pass the pointer to the freed object to cutworm().  Remember the
relevant weapon attribute before using and maybe freeing the object,
then pass that attribute instead of the whole weapon.  Also pass
'more-likely-to-cut' for axes in addition to blades.

thimonst() behaved similarly, although due to much different code
paths none of the objects that might get to hmon() were then passed to
cutworm(), so it wasn't vulnerable.  But pass 'more-likely-to-cut'
for axes instead of for blades when thrown.