Fix string substitution syntax

Signed-off-by: Olivier Aubert <olivier.aubert@liris.cnrs.fr>
Update generated module (against 2.0.1 headers)
Remove debug code
Define class conversion for log subscriber API
Implement FILE_ptr ctypes wrapper
Replace dump_enums/dump_funcs methods by generic dump() method
Implement callbacks wrapping

Define decorators to wrap callback methods that can be called from libvlc.
python bindings: fix docstring
Update generated module
python bindings: PyFile_FromFile/AsFile are removed in python3. Use PyFile_FromFd/PyObject_AsFileDescriptor
python: make test.py python3 compliant
python bindings: define common types/methods to unify string handling between python2 and 3

It does not properly solve all issues. Basically: python3 now treats
all strings as unicode strings, but the ctypes API conversion for
char* (ctypes.c_char_p) is mapped to byte strings. An explicit
conversion has to occur, but we have to specify the appropriate
encoding, which is hard to guess.
python bindings: automatically convert strings to bytes for python3
python bindings: getch() returns a string, there is no decode() method
python bindings: explicitly convert string to bytes
python bindings: blacklist libvlc_printerr for now
python bindings: convert string to bytes in logger test
python bindings: define test3 target for python3 bindings test
python bindings: fix print invocation
python bindings: iterators API now requires the __next__() method instead of next()

Implement both so that the code is python2+3 compatible