0.9.7.37:

        Make asdf-install use bivalent streams

        * Fix warnings and style-warnings when compiling a-i/installer.lisp:
          remove undefined variables / exported symbols *verify-gpg-signatures*
          and *safe-url-prefixes*, add a few ignored declarations.
        * Add :element-type :default to stream opening forms that need it
        * Allow sb-executable's copy-stream to deal with bivalent streams:
          Add an element-type &key argument that should be passed when copying
          bivalent streams