unix: add missing constants used with struct Timex on Linux

This provides definitions for Linux of two groups of constants,
which are used with struct Timex (used with the adjtimex and
clock_adjtime system calls): the ADJ_* constants are used
for the modes field; the STA_* constants are used for the status
field. The constants are documented in the adjtimex(2) man page.

Fixes golang/go#58012

Change-Id: I054f0c40f9cfd9360a0bb10716a08e19584c0fff
Reviewed-on: https://go-review.googlesource.com/c/sys/+/464241
Run-TryBot: Tobias Klauser <[email protected]>
Reviewed-by: Tobias Klauser <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Auto-Submit: Tobias Klauser <[email protected]>

unix/linux/types.go

@@ -477,6 +477,41 @@ type ItimerSpec C.struct_itimerspec
 
 type Itimerval C.struct_itimerval
 
+const (
+	ADJ_OFFSET            = C.ADJ_OFFSET
+	ADJ_FREQUENCY         = C.ADJ_FREQUENCY
+	ADJ_MAXERROR          = C.ADJ_MAXERROR
+	ADJ_ESTERROR          = C.ADJ_ESTERROR
+	ADJ_STATUS            = C.ADJ_STATUS
+	ADJ_TIMECONST         = C.ADJ_TIMECONST
+	ADJ_TAI               = C.ADJ_TAI
+	ADJ_SETOFFSET         = C.ADJ_SETOFFSET
+	ADJ_MICRO             = C.ADJ_MICRO
+	ADJ_NANO              = C.ADJ_NANO
+	ADJ_TICK              = C.ADJ_TICK
+	ADJ_OFFSET_SINGLESHOT = C.ADJ_OFFSET_SINGLESHOT
+	ADJ_OFFSET_SS_READ    = C.ADJ_OFFSET_SS_READ
+)
+
+const (
+	STA_PLL       = C.STA_PLL
+	STA_PPSFREQ   = C.STA_PPSFREQ
+	STA_PPSTIME   = C.STA_PPSTIME
+	STA_FLL       = C.STA_FLL
+	STA_INS       = C.STA_INS
+	STA_DEL       = C.STA_DEL
+	STA_UNSYNC    = C.STA_UNSYNC
+	STA_FREQHOLD  = C.STA_FREQHOLD
+	STA_PPSSIGNAL = C.STA_PPSSIGNAL
+	STA_PPSJITTER = C.STA_PPSJITTER
+	STA_PPSWANDER = C.STA_PPSWANDER
+	STA_PPSERROR  = C.STA_PPSERROR
+	STA_CLOCKERR  = C.STA_CLOCKERR
+	STA_NANO      = C.STA_NANO
+	STA_MODE      = C.STA_MODE
+	STA_CLK       = C.STA_CLK
+)
+
 const (
 	TIME_OK    = C.TIME_OK
 	TIME_INS   = C.TIME_INS