[vte] pty: Add link to some docs

[Christian Persch <chpe src gnome org>]

commit 12097b6c5135745de8cc756e02cad16f536cb33e
Author: Christian Persch <chpe src gnome org>
Date:   Mon Apr 27 20:49:04 2020 +0200

    pty: Add link to some docs

 src/pty.cc | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/src/pty.cc b/src/pty.cc
index 040a0005..79ab1b64 100644
--- a/src/pty.cc
+++ b/src/pty.cc
@@ -169,15 +169,19 @@ Pty::get_peer() const noexcept
         assert(bool(peer_fd));
 
 #if defined(__sun) && defined(HAVE_STROPTS_H)
+        /* See https://illumos.org/man/7i/streamio */
         if (isastream (peer_fd.get()) == 1) {
+                /* https://illumos.org/man/7m/ptem */
                 if ((ioctl(peer_fd.get(), I_FIND, "ptem") == 0) &&
                     (ioctl(peer_fd.get(), I_PUSH, "ptem") == -1)) {
                         return {};
                 }
+                /* https://illumos.org/man/7m/ldterm */
                 if ((ioctl(peer_fd.get(), I_FIND, "ldterm") == 0) &&
                     (ioctl(peer_fd.get(), I_PUSH, "ldterm") == -1)) {
                         return {};
                 }
+                /* https://illumos.org/man/7m/ttcompat */
                 if ((ioctl(peer_fd.get(), I_FIND, "ttcompat") == 0) &&
                     (ioctl(peer_fd.get(), I_PUSH, "ttcompat") == -1)) {
                         return {};