pgsql: Make parameters in implementation have same const:ness as the

Log Message:
-----------
Make parameters in implementation have same const:ness as the ones in
the prototype. Silences msvc build warning.

Modified Files:
--------------
pgsql/src/interfaces/libpq:
fe-lobj.c (r1.65 -> r1.66)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-lobj.c?r1=1.65&r2=1.66)