This routine decodes a string containing a numeric value. The decoded datum
is stored as an integer value. If a decoding error is detected, a warning
message is printed and an error status value is returned. A warning message
is printed if extra data follows the requested value (this data is ignored).
Parameters
<- int STdec1int
Error status,
0 - no error
1 - error, too few values or data format error
2 - warning, data values too large or too small
-> const char String[]
Input string
<- int *Ival
Returned value. This value is not changed if an error status is
returned.