syscall: wasi: more complete list of signals

Grepped straight out of the appropriate signal.h, with order preserved.

Makes 1.18 tests happier.

See comment on discrepancy for SIGCHLD.  Since wasi doesn't really support signals, this may not matter.

src/syscall/syscall_libc_wasi.go

@@ -9,16 +9,24 @@ import (
 )
 
 // https://github.com/WebAssembly/wasi-libc/blob/main/expected/wasm32-wasi/predefined-macros.txt
+// disagrees with ../../lib/wasi-libc/libc-top-half/musl/arch/wasm32/bits/signal.h for SIGCHLD?
+// https://github.com/WebAssembly/wasi-libc/issues/271
 
 type Signal int
 
 const (
-	SIGCHLD Signal = 16
 	SIGINT  Signal = 2
-	SIGKILL Signal = 9
-	SIGTRAP Signal = 5
 	SIGQUIT Signal = 3
+	SIGILL  Signal = 4
+	SIGTRAP Signal = 5
+	SIGABRT Signal = 6
+	SIGBUS  Signal = 7
+	SIGFPE  Signal = 8
+	SIGKILL Signal = 9
+	SIGSEGV Signal = 11
+	SIGPIPE Signal = 13
 	SIGTERM Signal = 15
+	SIGCHLD Signal = 17
 )
 
 func (s Signal) Signal() {}