Silence strncpy warning for gcc 8

[siddhesh]

The length in strncpy is one char too short and as a result it leads
to a build warning with gcc 8. bump up the length by one to copy the
NULL char.

[the-knights-who-say-ni]

Hello, and thanks for your contribution!

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[siddhesh]

I signed the CLA a couple of days ago, do I have to do something more to get the flag flipped?

[zhangyangyu]

I couldn't get the warning because Python applies -O:

/opt/bin/gcc -c -Wall -IInclude -I. Python/pystrtod.c
Python/pystrtod.c: In function ‘format_float_short’:
Python/pystrtod.c:1063:13: warning: ‘strncpy’ output truncated before terminating nul copying 3 bytes from a string of the same length [-Wstringop-truncation]
             strncpy(p, "ERR", 3);
             ^~~~~~~~~~~~~~~~~~~~
/opt/bin/gcc -c -O3 -Wall -IInclude -I. Python/pystrtod.c
/opt/bin/gcc -c -Og -Wall -IInclude -I. Python/pystrtod.c

But I think it's okay to just comment out the line.

[siddhesh]

Done, commented out since the next line aborts anyway.

[bedevere-bot]

@zhangyangyu: Please replace # with GH- in the commit message next time. Thanks!

[zhangyangyu]

Since Python's Makefile applies -O I only merge it with master branch. Thanks for your contribution @siddhesh :-)