veyron/runtimes/google/ipc/stream/crypto: Used the forked crypto/tls for Go versions <1.4

See the description of https://veyron-review.googlesource.com/#/c/3895/ for more details
(Or, git show --shortstat 18b2c2adfb46f8db99b66fc9351f6e50913214c6)

This commit implements steps (2) and (3) of the process described therein.

Change-Id: I230120674211daa88a436f579ada693144df72d4
diff --git a/runtimes/google/ipc/stream/crypto/tls_generate_old.sh b/runtimes/google/ipc/stream/crypto/tls_generate_old.sh
new file mode 100755
index 0000000..0560c33
--- /dev/null
+++ b/runtimes/google/ipc/stream/crypto/tls_generate_old.sh
@@ -0,0 +1,32 @@
+#!/bin/bash
+
+# This script generates a version of tls.go that can be built with Go compilers
+# prior to version 1.4.
+
+source "${VEYRON_ROOT}/environment/scripts/lib/shell.sh"
+
+main() {
+  local -r DIR="$(dirname "$0")"
+  local -r INFILE="${DIR}/tls.go"
+  local OUTFILE="${DIR}/tls_old.go"
+  [[ "$#" -gt 0 ]] && OUTFILE="$1"
+  readonly OUTFILE
+
+  cat <<EOF >$OUTFILE
+// THIS IS NOT THE FILE YOU WANT.
+// DO NOT EDIT THIS FILE.
+//
+// This file has been generated using the tls_generate_old.sh script.
+// Please do NOT make edits to this file. Instead edit tls.go and
+// use the script to regenerate this file
+
+EOF
+  cat "${INFILE}" |
+    sed -e 's|// +build go1.4|// +build !go1.4|' |
+    sed -e 's|"crypto/tls"|tls "veyron/runtimes/google/ipc/stream/crypto/tlsfork"|' >>$OUTFILE
+
+  local -r REPO_ROOT="$(git rev-parse --show-toplevel)"
+  "${REPO_ROOT}/scripts/build/go" fmt "${OUTFILE}"
+}
+
+main "$@"