Where strncat() is called with a fixed string source, increase the size by one.

Where strncat() is called with a fixed string source, increase the size by one.

GCC version 8 introduced some new warnings on strncat() usage in an
effort to warn about unsafe usage.  When the source string is a constant
literal and there will always be enough space in the destination, then
you could safely use strcat().  But lots of error-checking processes
will balk at ANY usage of strcat().  Given all this, putting a size of
something greater than the source will cause no harm.

See https://github.com/gcc-mirror/gcc/commit/d8aad7864e5b4c654dcea86b98085baf36d8db76