Fix for incorrect translation of empty strings
In the key change menu, when a button key not have name an empty string is passed to gettext.
The empty string is reserved for gettext to return de header of the .po file an this is shoved in the button
Fixes #4446: a syntax error that happens if something else (such as
<iomanip> or <locale> in certain libstdc++ versions) includes
<libintl.h> later, which contains a function declaration for gettext
that gets mangled by the macro.
See the added comment in gettext.h and the discussion in #4446/#4452
for details.
Everywhere where wstrgettext was used, its output was converted back
to utf8. As wstrgettext internally converts the return value
from utf8 to wstring, it has been a waste. Remove the function, and
use strgettext instead.
Use wide_to_utf8 and utf8_to_wide instead of wide_to_narrow and narrow_to_wide at almost all places.
Only exceptions: test functions for narrow conversion, and chat, which is done in a separate commit.
Two new configuration options are added:
- "enable_ipv6" to enable/disable the overall use of IPv6
- "ipv6_server" to enable/disable the use of IPv6 sockets when running
a server (when "enable_ipv6" is enabled)
Now the user-level option is called ENABLE_GETTEXT, and USE_GETTEXT is
only set to true if gettext was enabled and found. This simplifies all
check to USE_GETTEXT only rather than the double checks for it being
enabled and found.
