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)

All usages of gettext() are converted to wchars, so let's factor this
into a single inline.

set locales to C because en_US not installed on some systems, only UTF-8 version and en_US.UTF-8 does not work.

Otherwise the USE_GETTEXT define might not be visible.

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.

Put the gettext init code in a macro and define it appropriately
depending on whether gettext is actually available or not.

fixed error if gettext is disabled

german translation file
and bashscript to update translations

german translation file
and bashscript to update translations