Add some decref + update README adding debugging notes

When using the debug build of python, assserts raises en freeze pyfcgi telling
a decref is run on a thing with visit count == 0....

README

@@ -16,3 +16,9 @@ or
 logging to file example :
 -------------------------
 -L '/tmp/foo.log;0xff;{datetime} {msg} {ident}'
+
+Debugging :
+-----------
+	$ ./configure PYTHON_CONFIG_PATH=/usr/bin/python3dm-config --enable-debug
+	$ make clean && make
+	$ valgrind --log-file=/tmp/val.log --trace-children=yes spawn-fcgi -d . -n -p 9000 -a 127.0.0.1 -- src/pyfcgi -S -e foo_pep333 -E entrypoint -L '/tmp/foo.log;0xff;{datetime} {msg} {ident}'

src/python_pyfcgi.c

@@ -124,6 +124,7 @@ void libpyfcgi_set_headers_buf()
 	}
 
 repr = PyObject_ASCII(libpyfcgi.headers);
+Py_INCREF(repr);
 pyfcgi_log(LOG_DEBUG, "Sending headers : '%s'", PyUnicode_AsUTF8(repr));
 Py_DECREF(repr);
 
@@ -134,6 +135,7 @@ Py_DECREF(repr);
 		pyfcgi_log(LOG_ERR, "Unable to get iterator from given headers");
 		return;
 	}
+	Py_INCREF(heads_iter);
 
 	n_head = 0;
 	buf_ptr = libpyfcgi.heads_buf; //buffer pointer
@@ -142,10 +144,12 @@ Py_DECREF(repr);
 	buf_off = 0; //buffer pointer offset
 	while((head_tuple = PyIter_Next(heads_iter)))
 	{
+		Py_INCREF(head_tuple);
 		head_seq = PySequence_Fast(head_tuple, "Headers element is not a sequence");
 		if((tsz = PySequence_Fast_GET_SIZE(head_seq)) != 2)
 		{
 			repr = PyObject_ASCII(head_tuple);
+			Py_INCREF(repr);
 			snprintf(errstr, 256,
 				"Headers element expected to have len == 2, but got len %ld for element %ld : %s", tsz, n_head, PyUnicode_AsUTF8(repr));
 			Py_DECREF(repr);
@@ -174,6 +178,7 @@ Py_DECREF(repr);
 					goto head_decode_err;
 				}
 			}
+			Py_INCREF(bytes[i]);
 			head_str[i] = PyBytes_AsString(bytes[i]);
 			
 		}
@@ -210,6 +215,8 @@ Py_DECREF(repr);
 		}
 
 		n_head++;
+		Py_DECREF(bytes[0]);
+		Py_DECREF(bytes[1]);
 		Py_DECREF(head_seq);
 		Py_DECREF(head_tuple);
 	}