poss-pron lex rules should have shared info on supertype

[emilymbender]

A set up like this leads to many types with repeated constraints that should ideally be pulled up onto a supertype:

section=adnom-poss
  poss-pron1_type=affix
  poss-pron1_agr=non-agree
  poss-pron1_mod-spec=spec


section=morphology
  noun-pc1_name=poss_inal_non1
  noun-pc1_obligatory=on
  noun-pc1_order=suffix
  noun-pc1_inputs=noun109, noun110
    noun-pc1_lrt1_name=poss_inalienable_2sg
      noun-pc1_lrt1_feat1_name=poss-pron1
      noun-pc1_lrt1_feat1_value=plus
      noun-pc1_lrt1_feat1_head=itself
      noun-pc1_lrt1_feat2_name=pernum
      noun-pc1_lrt1_feat2_value=2sg
      noun-pc1_lrt1_feat2_head=possessor
      noun-pc1_lrt1_lri1_inflecting=yes
      noun-pc1_lrt1_lri1_orth=-m
    noun-pc1_lrt2_name=poss_inalienable_3sg
      noun-pc1_lrt2_feat1_name=poss-pron1
      noun-pc1_lrt2_feat1_value=plus
      noun-pc1_lrt2_feat1_head=itself
      noun-pc1_lrt2_feat2_name=pernum
      noun-pc1_lrt2_feat2_value=3sg
      noun-pc1_lrt2_feat2_head=possessor
      noun-pc1_lrt2_lri1_inflecting=yes
      noun-pc1_lrt2_lri1_orth=-n