pgsql: We only need to add thread.c on non-WIN32 platforms, since

Log Message:
-----------
We only need to add thread.c on non-WIN32 platforms, since get_home_path
doesn't use pqGetpwuid on WIN32.  Rather than try to figure out why it
won't build on WIN32, just remove it.

Modified Files:
--------------
    pgsql/src/interfaces/ecpg/ecpglib:
        Makefile (r1.39 -> r1.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/Makefile.diff?r1=1.39&r2=1.40)