Add a mips64 big endian target to test.
With the proliferation of tests subdirs, WITHOUT_TESTS is now required as we don't want these.  Fixes build on head.
Add libxo for df as it is now required.
Add libgpio to the build  now.  Note that libxo is required by at least df
tools for ap93.
Merge pull request #19 from erikarn/master

Add a mips64 big endian target to test.