Returning non-terminated string in ECPG Informix-compatible function

Greetings, everyone!

While analyzing output of Svace static analyzer [1] I've found a bug.

In function intoasc(interval * i, char *str) from file 
src/interfaces/ecpg/compatlib/informix.c
we return a non-terminated string since we use memcpy on tmp which is 
itself NULL-teminated but
last zero byte is not copied.

The proposed solution is to use strcpy instead, since it is used in all 
other functions in informix.c.

The patch is attached.

[1] - https://svace.pages.ispras.ru/svace-website/en/

Oleg Tselebrovskiy, Postgres Pro