When setting a syscall catchpoint by name, catch syscalls whose name
or alias matches the requested string.
When the ABI of a system call is changed in the FreeBSD kernel, this
is implemented by leaving a compatibility system call using the old
ABI at the existing "slot" and allocating a new system call for the
version using the new ABI. For example, new fields were added to the
'struct kevent' used by the kevent() system call in FreeBSD 12. The
previous kevent() system call in FreeBSD 12 kernels is now called
freebsd11_kevent() and is still used by older binaries compiled
against the older ABI. The freebsd11_kevent() system call can be
tagged with an "alias" attribute of "kevent" permitting 'catch syscall
kevent' to catch both system calls and providing the expected user
behavior for both old and new binaries. It also provides the expected
behavior if GDB is compiled on an older host (such as a FreeBSD 11
host).