sigsegv-tests: port to plain POSIX * tests/test-sigsegv-catch-segv1.c, tests/test-sigsegv-catch-segv2.c: (SIGSEGV_FAULT_ADDRESS_ROUNDOFF_BITS): Use sysconf (_SC_PAGESIZE) instead of getpagesize, as this code is compiled only on platforms that have _SC_PAGESIZE and POSIX prefers the latter.