buildsys: remove some obsolete optimization CFLAGS

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
mips: rename siginfo _timer members

Rename _timer[12] to si_tid and si_overrun to fix compilation of
strace-4.9+

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>