Update contrib/redhat/openssh.spec file

Updates are in the %changelog, and include:

* Add '--mandir' and '--with-mantype' for RHEL 5 compatibility
* Add 'dist' option to 'ver' so package names reflect OS at build time
* Always include x11-ssh-askpass tarball in SRPM
* Add openssh-x11-aspass BuildRequires for libXT-devel, imake, gtk2-devel
* Discard 'K5DIR' reporting, not usable inside 'mock' for RHEL 5 compatibility
* Discard obsolete '--with-rsh' configure option
* Update openssl-devel dependency to 0.9.8f, as found in autoconf