tons of fixes for the test suite: docstrings must be unicode strings to run in Py3's doctest (obviously...)

--HG--
rename : tests/compile/withnogil.pyx => tests/run/withnogil.pyx

make it explicit in the generated source code what is an identifier string constant and what is a normal string constant that just happens to get interned

support running tests without running Cython to test the generated code under different Python versions (including Py3)

put the annotated .html file next to the .c file to fix annotation when the .c file is not in the same directory as the .pyx file