Set up a default INSTALLDIR.

Set up a default INSTALLDIR.

Various scripts fail horribly without this - most notably the editing script, but also keygen.
This only get provoked by a GUI-less install but should work anyway.

Hard wire the default to be C:\opt\shibboleth-sp\ Unfortunately we have to hardwire the dos device
since symbol exampansion does not work, and without a dos device we wonder off into network territory.

git-svn-id: https://svn.shibboleth.net/cpp-sp/branches/REL_2@3857 cb58f699-b61c-0410-a6fe-9272a202ed29