[Bug middle-end/63510] Wrong line number in Wstrict-overflow message

[gang.chen.5i5j at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63510

--- Comment #9 from Chen Gang <gang.chen.5i5j at gmail dot com> ---
We need call warning_at() instead of warnings() in fold_overflow_warning() in
gcc/fold-const.c.

The related location parameter of warning_at() should be calculated, just like
another gcc files has done: e.g. gcc/c-family/*.c which use warning_at().

I shall continue to analyze how to calculate the location in gcc/fold-const.c,
reference from the other files.

Thanks.