pgsql: Change Win32 dlerror message to: return "dynamic loading

Log Message:
-----------
Change Win32 dlerror message to:

return "dynamic loading error";

Modified Files:
--------------
pgsql/src/backend/port/dynloader:
win32.c (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/dynloader/win32.c.diff?r1=1.4&r2=1.5)