[Bug Fix]ECPG: cancellation of significant digits on ECPG

Hi,
Currently our customer uses PostgreSQL 9.6 and hits ECPG's bug during using numeric data type by SQLDA.
I confirmed that this problem is occurred on master and 9.6 latest branch.

PROBLEM
---------------------------------------
When the integer part of numeric data type is "0", cancellation of significant digits is occurred.
For example, I expect "0.12345", but I got "0.12340". When I expect "0.01234", I got "0.01200"
I attached the sample application code to reproduce this problem.

CAUSE
---------------------------------------
When copy the data of numeric data, the size is wrong.
"src/interfaces/ecpg/ecpglib/sqlda.c" has problem.

ecpg_set_native_sqlda(int lineno, struct sqlda_struct ** _sqlda, const PGresult *res, int row, enum COMPAT_MODE compat)
{
...
if (num->ndigits)
{
ecpg_sqlda_align_add_size(next_offset, sizeof(int), num->ndigits + 1, &offset, &next_offset);
memcpy((char *) sqlda + offset, num->buf, num->ndigits + 1);

((numeric *) sqlda->sqlvar[i].sqldata)->buf = (NumericDigit *) sqlda + offset;
((numeric *) sqlda->sqlvar[i].sqldata)->digits = (NumericDigit *) sqlda + offset + (num->digits - num->buf);
}
...

When numeric data is "0.12345", num->buf has "0 0 1 2 3 4 5" and num->digits has "1 2 3 4 5".
num->ndigits has the number of digits which is or later "1", it means 5.

In this code, currently copy "num->ndigits + 1" as size of numeric data.
As a result, (char *) sqlda + offset has "0 0 1 2 3 4", not "0 0 1 2 3 4 5".
So, "num->digits - num->buf + num->ndigits" should be copied.

FIX
---------------------------------------
Above source code should be fixed and other similar bugs are fixed too.
I attached patches for bug fix and regression test for master branch.
I hope this bug fix will be backport to other versions.

Regards,
Daisuke Higuchi