Made parser check for valid copy to/from stdin/stdout combinations.

src/interfaces/ecpg/ChangeLog

src/interfaces/ecpg/ecpglib/data.c

src/interfaces/ecpg/ecpglib/misc.c

src/interfaces/ecpg/preproc/preproc.y

src/interfaces/ecpg/test/errors/init.pgc

...s/ecpg/test/expected/compat_informix-test_informix.stderr

.../ecpg/test/expected/compat_informix-test_informix2.stderr

src/interfaces/ecpg/test/expected/complex-test1.stderr

src/interfaces/ecpg/test/expected/complex-test2.stderr

src/interfaces/ecpg/test/expected/complex-test3.stderr

src/interfaces/ecpg/test/expected/complex-test4.stderr

src/interfaces/ecpg/test/expected/complex-test5.stderr

src/interfaces/ecpg/test/expected/connect-test2.stderr

src/interfaces/ecpg/test/expected/connect-test3.stderr

src/interfaces/ecpg/test/expected/errors-init.c

src/interfaces/ecpg/test/expected/errors-init.stderr

src/interfaces/ecpg/test/expected/errors-init.stdout

src/interfaces/ecpg/test/expected/pgtypeslib-dt_test.stderr

src/interfaces/ecpg/test/expected/pgtypeslib-num_test.stderr

src/interfaces/ecpg/test/expected/sql-define.stderr