Added some more informix compatibility functions.

src/interfaces/ecpg/ChangeLog

src/interfaces/ecpg/compatlib/informix.c

src/interfaces/ecpg/ecpglib/connect.c

src/interfaces/ecpg/include/ecpglib.h

src/interfaces/ecpg/pgtypeslib/datetime.c

src/interfaces/ecpg/preproc/ecpg.c