Update to linux_tools

Modernizes viewer_manifest.py
adds install.sh and refresh_desktop_app_entry.sh for those who want to "install" Singularity to their applications.
Updates client-readme-voice.txt to explain about Multi-Voice

indra/newview/linux_tools/refresh_desktop_app_entry.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+SCRIPTSRC=`readlink -f "$0" || echo "$0"`
+RUN_PATH=`dirname "${SCRIPTSRC}" || echo .`
+
+install_prefix=${RUN_PATH}
+
+function install_desktop_entry()
+{
+    local installation_prefix="$1"
+    local desktop_entries_dir="$2"
+
+    local desktop_entry="\
+[Desktop Entry]\n\
+Name=Singularity\n\
+Comment=Client for Online Virtual Worlds, such as Second Life\n\
+Exec=${installation_prefix}/singularity\n\
+Icon=${installation_prefix}/singularity_icon.png\n\
+Terminal=false\n\
+Type=Application\n\
+Categories=Application;Network;\n\
+StartupNotify=true\n\
+X-Desktop-File-Install-Version=3.0"
+
+    echo " - Installing menu entries in ${desktop_entries_dir}"
+    mkdir -vp "${desktop_entries_dir}"
+    echo -e $desktop_entry > "${desktop_entries_dir}/singularity-viewer.desktop" || "Failed to install application menu!"
+}
+
+if [ "$UID" == "0" ]; then
+    # system-wide
+    install_desktop_entry "$install_prefix" /usr/local/share/applications
+else
+    # user-specific
+    install_desktop_entry "$install_prefix" "$HOME/.local/share/applications"
+fi