unix: add Msync function on Solaris

Add the Msync function on solaris/amd64.

Change-Id: Idde0f9e693f924fef471acb42afb84e83c4cee76
Reviewed-on: https://go-review.googlesource.com/64370
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_solaris.go

@@ -612,6 +612,7 @@ func IoctlGetTermio(fd int, req uint) (*Termio, error) {
 //sys	Mlock(b []byte) (err error)
 //sys	Mlockall(flags int) (err error)
 //sys	Mprotect(b []byte, prot int) (err error)
+//sys	Msync(b []byte, flags int) (err error)
 //sys	Munlock(b []byte) (err error)
 //sys	Munlockall() (err error)
 //sys	Nanosleep(time *Timespec, leftover *Timespec) (err error)

unix/zsyscall_solaris_amd64.go

@@ -75,6 +75,7 @@ import (
 //go:cgo_import_dynamic libc_mlock mlock "libc.so"
 //go:cgo_import_dynamic libc_mlockall mlockall "libc.so"
 //go:cgo_import_dynamic libc_mprotect mprotect "libc.so"
+//go:cgo_import_dynamic libc_msync msync "libc.so"
 //go:cgo_import_dynamic libc_munlock munlock "libc.so"
 //go:cgo_import_dynamic libc_munlockall munlockall "libc.so"
 //go:cgo_import_dynamic libc_nanosleep nanosleep "libc.so"
@@ -195,6 +196,7 @@ import (
 //go:linkname procMlock libc_mlock
 //go:linkname procMlockall libc_mlockall
 //go:linkname procMprotect libc_mprotect
+//go:linkname procMsync libc_msync
 //go:linkname procMunlock libc_munlock
 //go:linkname procMunlockall libc_munlockall
 //go:linkname procNanosleep libc_nanosleep
@@ -316,6 +318,7 @@ var (
 	procMlock,
 	procMlockall,
 	procMprotect,
+	procMsync,
 	procMunlock,
 	procMunlockall,
 	procNanosleep,
@@ -1017,6 +1020,18 @@ func Mprotect(b []byte, prot int) (err error) {
 	return
 }
 
+func Msync(b []byte, flags int) (err error) {
+	var _p0 *byte
+	if len(b) > 0 {
+		_p0 = &b[0]
+	}
+	_, _, e1 := sysvicall6(uintptr(unsafe.Pointer(&procMsync)), 3, uintptr(unsafe.Pointer(_p0)), uintptr(len(b)), uintptr(flags), 0, 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
 func Munlock(b []byte) (err error) {
 	var _p0 *byte
 	if len(b) > 0 {