ssh/terminal: use "reports whether" in IsTerminal doc

Go documentation style for boolean funcs is to say:

    // Foo reports whether ...
    func Foo() bool

(rather than "returns true if")

Change-Id: I6972d123ba99bbf3dbf95e876b45b2ecd98dd07c
Reviewed-on: https://go-review.googlesource.com/c/151257
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

util.go

@@ -25,7 +25,7 @@ type State struct {
 	termios unix.Termios
 }
 
-// IsTerminal returns true if the given file descriptor is a terminal.
+// IsTerminal returns whether the given file descriptor is a terminal.
 func IsTerminal(fd int) bool {
 	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
 	return err == nil

util_plan9.go

@@ -21,7 +21,7 @@ import (
 
 type State struct{}
 
-// IsTerminal returns true if the given file descriptor is a terminal.
+// IsTerminal returns whether the given file descriptor is a terminal.
 func IsTerminal(fd int) bool {
 	return false
 }

util_solaris.go

@@ -17,7 +17,7 @@ type State struct {
 	termios unix.Termios
 }
 
-// IsTerminal returns true if the given file descriptor is a terminal.
+// IsTerminal returns whether the given file descriptor is a terminal.
 func IsTerminal(fd int) bool {
 	_, err := unix.IoctlGetTermio(fd, unix.TCGETA)
 	return err == nil

util_windows.go

@@ -26,7 +26,7 @@ type State struct {
 	mode uint32
 }
 
-// IsTerminal returns true if the given file descriptor is a terminal.
+// IsTerminal returns whether the given file descriptor is a terminal.
 func IsTerminal(fd int) bool {
 	var st uint32
 	err := windows.GetConsoleMode(windows.Handle(fd), &st)