Add openssl-dev and xorg-x11-dev to README

Attached is a documentation patch to the top-level README file; it
just adds two notes saying that you need to have openssl-devel and
xorg-x11-devel installed to successfully complete a "make world" at
the top level.

Signed-off-by: Chris Lalancette <clalance@redhat.com>

README

@@ -92,6 +92,8 @@ provided by your Linux distributor:
     * Development install of zlib (e.g., zlib-dev)
     * Development install of Python v2.3 or later (e.g., python-dev)
     * Development install of curses (e.g., libncurses-dev)
+    * Development install of openssl (e.g., openssl-dev)
+    * Development install of x11 (e.g. xorg-x11-dev)
     * bridge-utils package (/sbin/brctl)
     * iproute package (/sbin/ip)
     * hotplug or udev