fix engraving with miscellaneous items

Reported directly to devteam:  when selecting an item to engrave
with, "getobj refactor"'s stylus_ok() classified none-of-the-above
objects as not viable instead of allowing arbitrary things to
engrave in the dust or give specific can't-use-that messages like
for food.  Make the suggested fix:  change default result when
checking an inventory item for applicability from GETOBJ_EXCLUDE
to GETOBJ_DOWNPLAY.

Engrave feedback rather than getobj selection:  splash of venom
isn't necessarily wizard mode-only so don't reject attempting to
engrave with it as using an illegal object.  And remove the extra
question mark from its "poison pen" message.

doc/fixes37.0

@@ -733,6 +733,7 @@ give genetic engineers teleport capability (as they had in slash'em); 'port
 if an invisible hero managed to convert an unaligned altar to an aligned one
 	with color enabled, altar wasn't immediately redrawn with new color
 repair some regressions to (a)pply introduced by "getobj refactor" patch
+getobj too: allow attempting to (E)ngrave with any item in inventory
 fix ^X feedback when held typo: "unseen createure" -> "unseen creature"
 if a <foo> corpse was set to revive as a <foo> zombie and corpse was partly
 	eaten at revival time and monster <foo> is defined as providing more