os: document the various enum values in os.Signal (#22770)

vlib/os/signal.v

@@ -7,37 +7,37 @@ module os
 // consult man pages / signal.h .
 
 pub enum Signal {
-	hup    = 1
-	int    = 2
-	quit   = 3
-	ill    = 4
-	trap   = 5
-	abrt   = 6
-	bus    = 7
-	fpe    = 8
-	kill   = 9
-	usr1   = 10
-	segv   = 11
-	usr2   = 12
-	pipe   = 13
-	alrm   = 14
-	term   = 15
-	stkflt = 16
-	chld   = 17
-	cont   = 18
-	stop   = 19
-	tstp   = 20
-	ttin   = 21
-	ttou   = 22
-	urg    = 23
-	xcpu   = 24
-	xfsz   = 25
-	vtalrm = 26
-	prof   = 27
-	winch  = 28
-	poll   = 29
-	pwr    = 30
-	sys    = 31
+	hup    = 1  // hangup
+	int    = 2  // interrupt from keyboard
+	quit   = 3  // quit from keyboard
+	ill    = 4  // illegal instruction
+	trap   = 5  // trace trap
+	abrt   = 6  // abort
+	bus    = 7  // bus error
+	fpe    = 8  // floating point exception
+	kill   = 9  // kill signal
+	usr1   = 10 // user-defined signal 1
+	segv   = 11 // segmentation violation
+	usr2   = 12 // user-defined signal 2
+	pipe   = 13 // write on a pipe with no one to read it
+	alrm   = 14 // alarm clock
+	term   = 15 // software termination signal
+	stkflt = 16 // stack fault
+	chld   = 17 // child process has stopped or exited
+	cont   = 18 // continue executing, if stopped
+	stop   = 19 // stop executing (cannot be caught or ignored)
+	tstp   = 20 // stop executing, can be caught and ignored
+	ttin   = 21 // terminal input for background process
+	ttou   = 22 // terminal output for background process
+	urg    = 23 // urgent condition on socket
+	xcpu   = 24 // CPU time limit exceeded
+	xfsz   = 25 // file size limit exceeded
+	vtalrm = 26 // virtual time alarm
+	prof   = 27 // profiling timer alarm
+	winch  = 28 // window size change
+	poll   = 29 // pollable event occurred
+	pwr    = 30 // power failure
+	sys    = 31 // bad system call
 }
 
 pub type SignalHandler = fn (Signal)