Updated x0vncserver to the latest version from the "tightvnc-unix"

Updated x0vncserver to the latest version from the "tightvnc-unix"
module. It includes support for overlay extensions under IRIX and
Solaris, MIT-SHM support, much improved polling algorithm and support
for IP filtering on accepting connections. However, current version
does not seem stable when linked with this codebase -- it is not
compatible with 1.3dev5 viewers for some reasons, and crashes on
"select: interrupted system call" from time to time. Also, the
"configure" script is not yet updated to enable certain features of
this version.

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@309 3789f03b-4d11-0410-bbf8-ca57d06f2519