gnu: Rename qtbase to qtbase-5.

gnu: Rename qtbase to qtbase-5.

This change was automated via the following command:

$ git ls-files | xargs sed -i 's/,qtbase)/,qtbase-5)/g'
$ git ls-files | xargs sed -i 's/inherit qtbase)/inherit qtbase-5)/g'
$ git ls-files | xargs sed -i 's/package-version qtbase)/package-version qtbase-5)/g'
$ git checkout etc    # to clear some spurious changes

This is done so the qtbase package can be upgraded to version 6 in the
following commit.