Libpq++ fixes for Win32 compile.

src/include/c.h

src/include/config.h.win32

src/interfaces/libpq++/pgconnection.h

src/interfaces/libpq++/pgcursordb.h

src/interfaces/libpq++/pgdatabase.h

src/interfaces/libpq++/pglobject.h

src/interfaces/libpq++/pgtransdb.h

src/win32.mak