tests: Support newer ncurses with italic caps in xterm terminfo
* tests/test-term-ostream-xterm-basic-italic.out: New file.
* tests/test-term-ostream-xterm: Use it as possible test result.
* Makefile.am (EXTRA_DIST): Add new files.
Needed for ncurses >= 5.9-20140906 that defines sitm/ritm in the
xterm-basic terminfo definition.
