libecpg versions and libecpg_compat

Hi list,

I've been building ECPG (embedded SQL/C) programs on a system with Pg
version 8.0 installed. When I tried to run them recently on version 8.4
I found that there was a libecpg library incompatibility: v8.0 uses
libecpg.so.5, whereas 8.4 uses libecpg.so.6.

Then I noticed libecpg_compat in the lib area. What is this used for?
"compat" suggests compatibility between different versions? But Pg 8.0
has libecpg_compat.so.2, whereas Pg 8.4 has libecpg_compat.so.3.

Is there some way of building with Pg v8.4 ECPG lib and running on a
system with Pg v8.0 ECPG lib? or vice versa? and is libecpg_compat
intended for that purpose?

Thanks,
Rob