in backtrace.c and diagnose.c - it's 3 because of the EBP/RBP register's
position in the jmp_buf
(https://github.com/freebsd/freebsd/blob/master/lib/libc/amd64/gen/_setjmp.S
and
https://github.com/freebsd/freebsd/blob/master/lib/libc/i386/gen/_setjmp.S).

Patch by: me

(cherry picked from commit 87451f66)

Change-Id: I5f18cd9145f90db351c124c6f914411f1ffc2a83