Use more accurate way of detecting ostruct members
Use more accurate way of detecting ostruct members

Fixes two tests on 1.8.7 and 1.9.2.

ctreatma/warbler,mkristian/warbler,idibon/warbler,fedenusy/warbler,fedenusy/warbler,idibon/warbler,idibon/warbler,mkristian/warbler,atambo/warbler,ctreatma/warbler,atambo/warbler,mkristian/warbler,ctreatma/warbler,fedenusy/warbler,idibon/warbler,fedenusy/warbler,ctreatma/warbler