Use correct function name to PyArg_ParseTuple("is_package").

Fix off-by-1 error in normalize_line_endings():
  when *p == '\0' the NUL was copied into q and q was auto-incremented,
  the loop was broken out of,
  then a newline was appended followed by a NUL.
  So the function, in effect, was strcpy() but added two extra chars
  which was caught by obmalloc in debug mode, since there was only
  room for 1 additional newline.

Get test working under regrtest (added test_main).