Fixed initialization bug and added postgres_fe.h to pgtypeslib.

src/interfaces/ecpg/compatlib/informix.c

src/interfaces/ecpg/pgtypeslib/common.c

src/interfaces/ecpg/pgtypeslib/datetime.c

src/interfaces/ecpg/pgtypeslib/dt_common.c

src/interfaces/ecpg/pgtypeslib/interval.c

src/interfaces/ecpg/pgtypeslib/numeric.c

src/interfaces/ecpg/pgtypeslib/timestamp.c