Hi,
This small patch implements a new GUC (default_index_tablespace) plus 
supporting code.
Originated from a customer request, the feature intends to make 
creation of indexes on SSD-backed tablespaces easy and convenient 
(almost transparent) for users: the DBA can just set it and indexes will 
be placed in the specified tablespace --as opposed to the same 
tablespace where the referenced table is-- without having to specify it 
every time.
Feedback appreciated.
Thanks,
   / J.L.