Error message FSUM7327 signal number 13 not conventional in various places

[MikeFultonDev]

Switch from working numbered signals such as 1, 2, 13, 15 to corresponding HUP, INT, PIPE, TERM

See at least:

• build-aux/config.guess
• configure

[MikeFultonDev]

When running test 15, this is printed to stderr:

> trap: ./configure 1577: FSUM7327 signal number 13 not conventional
> trap: ./config.status 542: FSUM7327 signal number 13 not conventional