Treat file names in POSIX-like case-sensitive fashion by default

Treat file names in POSIX-like case-sensitive fashion by default

*** THIS COMMIT CAUSES A CHANGE OF DEFAULT BEHAVIOR IN libsmbclient!!! ***

- libsmbclient now calls cli_set_case_sensitive() for a new CLI. By default,
  it requests case-sensitive, but the old behavior of case-insensitive can be
  requested with smbc_setOptionCaseSensitive(context, False);

  The change of behavior is considered a bug fix, as it was previously
  possible to accidentally overwrite a file that had the same case-insensitive
  name but a different case-sensitive name as a previously-existing file,
  while creating a new file.

Derrell