Fix #8: Set *default-pathname-defaults* for cmucl.
Set `*default-pathname-defaults*` for cmucl in `gclload1.lsp` so that it has the full path to `gclload.lsp`. This is needed so that the tests can be loaded from the subdirectories. Without this, each load file in the subdirectory is set to #P"" and when it tries to load a test file, it can't because the setting of `*default-pathname-defaults*` isn't pointing to the subdirectory but rather the main directory since #P"" means current directory, and cmucl hasn't changed it's current directory. This fix only applies to cmucl and no other lisps.