report filenames relative to the current directory or as absolute paths i

we use relative filenames for files in the directory itself or
subdirectories, absolute paths otherwise.

this makes cython compatible with emacs compilation mode.

fix PEP-393 error case in __Pyx_UnicodeContainsUCS4() by handling all possible cases separately; clean up redundant code

implement __Pyx_UnicodeContainsUCS4() for PEP 393, mark places that currently swallow errors for later fixing

--HG--
extra : rebase_source : aafa348ec2c8713dfa8635c17e5d11db3b05f30b

--HG--
extra : rebase_source : 9be73c313cb44d6c7485ca9288382c9ad2614a45

--HG--
extra : rebase_source : 211fa0c1058750151e3524d4ca5854a86ed5289f

update to wrapping c++ documentation

Acquire the GIL to build the traceback in nogil functions