Change the return type of jsonObjectGetString so that it

Change the return type of jsonObjectGetString so that it
is a pointer to const char, instead of to non-const char.

We don't want the calling code to be able to modify the innards
of the jsonObject, at least not by this back door.

I have already examined all uses of this function and modified
them where necessary to avoid compile problems.

M    include/opensrf/osrf_json.h
M    src/libopensrf/osrf_json_object.c

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1803 9efc2488-bf62-4759-914b-345cdb29e865