Add syntax-check rule against CPU predef misspellings. * lib/getloadavg.c: Test __alpha, not __alpha__. * tests/test-snan-2.c: Likewise. * m4/exponentd.m4: Test __arm__, not __arm. * lib/utimensat.c: Test __hppa, not __hppa__. * tests/qemu.h: Likewise. * lib/fma.c: Test __sparc, not __sparc__. * tests/qemu.h: Likewise. * tests/test-exp2.h: Likewise. * tests/test-nonblocking-pipe.h: Likewise. * tests/test-snan-1.c: Likewise. * tests/test-snan-2.c: Likewise.