4e40dc538c
Previously abort() called core::intrinsics::abort() which compiles to the ud2 instruction, generating an Invalid Opcode fault. The kernel logs this as 'UNHANDLED EXCEPTION' and kills the process, but the fault message is alarming and doesn't reflect the actual intent (SIGABRT from process self-termination). This change uses the POSIX-compliant abort sequence: raise(SIGABRT) first (default handler terminates the process), then _Exit(134) as fallback if the signal handler returns. Six sites updated: stdlib abort, assert __assert_fail, lib.rs relibc_panic/oom/_Unwind_Resume, start.rs relibc_verify_host. The proc-manager-fallback in redox-rt/src/sys.rs retains core::intrinsics::abort() — that path is a true 'system unreachable' last resort where raise/_Exit cannot succeed.