Add support for IPv6 to cacaserver

Disable cppunit  tests by default, honor --enable-cppunit

Bold/italic attribute support for export to svg

slang driver: enable utf8 auto-detection (bug fix)

These were all caused by sprintf() appending a null char that was not actually used.
Fixes CVE-2021-30498 and CVE-2021-30499.

Fixes: #52 (CVE-2021-3410)

Fixes: #42

Fixes: #38 (CVE-2018-20546)
Fixes: #39 (CVE-2018-20547)

Fixes: #37 (CVE-2018-20545)
Fixes: #40 (CVE-2018-20548)
Fixes: #41 (CVE-2018-20549)

Fixes: #36 (CVE-2018-20544)

Hide private symbols (issue #33).

The slang internal auto-detection of utf8 is only executed by a call to
SLutf8_enable(-1).

This will hopefully fix the OS X ruby package.

Fix a bug into the autorepeat trigger.

- Only affect slang/ncurses.

Issue #15: Fix returned pointer with caca types.

Fixed VS2015 error; snprintf std is now included

The Xlib and ncurses libraries query the LC_CTYPE locale value to guess
the usable character set. If the calling program did not call setlocale(),
that character set will be severely limited. Extensive Unicode support
is a reasonable libcaca user expectation.

The locale is restored as soon as possible, once the window or terminal
have been initialised. Unfortunately, the effect of setlocale() is process-
wide, and may affect other threads. This is now documented.

Note also that both Xlib and ncurses ignore the effects of uselocale()
which would have been the thread-safe solution to this problem.