More tinkering with oils_cstore.c:

More tinkering with oils_cstore.c:

1. In a couple of spots: replaced jsonObjectClone() with
jsonObjectExtractIndex(), so that we can use an existing
object instead of copying it.

2. In verifyObjectClass(): protected against formatting a NULL
into an error message.

3. In verifyObjectPCRUD(): eliminated a pointless strdup().

4. Rearranged doRetrieve() a bit for clarity, and renamed some
variables for the same reason.  Also added a couple of comments.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@13513 dcc99617-32d9-48b4-a31d-7c20da2025e4