macos: packaging support for MacOS X 10.15

This commit introduces the new set of changes / files required to
successfully create the dmg installer on OS X 10.15 "Catalina".

Change-Id: I628a3210fa42b2f34ff78030930f83e836775392
Reviewed-on: https://gerrit.openafs.org/13669
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>

src/packaging/MacOS/InstallationCheck.19

@@ -0,0 +1,19 @@
+#!/bin/sh
+majorvers=`uname -r | sed 's/\..*//'`
+if [ $majorvers -ne 19 ]; then
+	exit 112
+fi
+
+# check for temporary versions of ThisCell and CellAlias
+# and move them aside
+tmpthiscell=/private/tmp/org.OpenAFS.Install.ThisCell.$USER
+tmpcellalias=/private/tmp/org.OpenAFS.Install.CellAlias.$USER
+date=`date +%Y%m%d%H%M`
+if [ -e $tmpthiscell ]; then
+    mv -f $tmpthiscell $tmpthiscell.$date
+fi
+if [ -e $tmpcellalias ]; then
+    mv -f $tmpcellalias $tmpcellalias.$date
+fi
+
+exit 0

src/packaging/MacOS/InstallationCheck.strings.19

@@ -0,0 +1 @@
+"16" = "This OpenAFS release requires Catalina (10.15)";

src/packaging/MacOS/ReadMe.rtf.19

@@ -0,0 +1,7 @@
+{\rtf1\ansi\ansicpg1252\cocoartf1038\cocoasubrtf320
+{\fonttbl\f0\fswiss\fcharset0 Helvetica;}
+{\colortbl;\red255\green255\blue255;}
+\margl1440\margr1440\vieww9000\viewh9000\viewkind0
+\pard\tx1440\tx2880\tx4320\tx5760\tx7200\ql\qnatural
+
+\f0\fs24 \cf0 This release of OpenAFS is targeted at MacOS 10.15 (Catalina) and is not recommended for use with any other version.}

src/packaging/MacOS/pkgbuild.sh.in

@@ -139,6 +139,10 @@ elif [ x"$majorvers" = x18 ]; then
     RELNAME="Mojave"
     THISREL=14
 
+elif [ x"$majorvers" = x19 ]; then
+    RELNAME="Catalina"
+    THISREL=15
+
 elif [ x"$majorvers" = x ] ; then
     echo "Error running uname" >&2
     exit 1