Use the full version string for the windows installer exe
Delete the installer exe when cleaning
auto merge of #11354 : brson/rust/versionwin, r=alexcrichton

The makefiles and the windows installer disagree on the name of this file. In practical terms this change only means that the '-pre' installers will be named 'rust-0.9-pre-install.exe' instead 'rust-0.9-install.exe'.