More patches for informix compatibility.

src/interfaces/ecpg/compatlib/informix.c

src/interfaces/ecpg/ecpglib/data.c

src/interfaces/ecpg/ecpglib/execute.c

src/interfaces/ecpg/include/decimal.h

src/interfaces/ecpg/include/pgtypes_date.h

src/interfaces/ecpg/include/pgtypes_error.h

src/interfaces/ecpg/include/pgtypes_interval.h

src/interfaces/ecpg/include/pgtypes_numeric.h

src/interfaces/ecpg/include/pgtypes_timestamp.h

src/interfaces/ecpg/pgtypeslib/common.c

src/interfaces/ecpg/pgtypeslib/datetime.c

src/interfaces/ecpg/pgtypeslib/dt.h

src/interfaces/ecpg/pgtypeslib/dt_common.c

src/interfaces/ecpg/pgtypeslib/extern.h

src/interfaces/ecpg/pgtypeslib/interval.c

src/interfaces/ecpg/pgtypeslib/numeric.c

src/interfaces/ecpg/pgtypeslib/timestamp.c