File t4k_common-c99.patch of Package t4k_common

GNULIB_UNISTR_U8_MBTOUC_UNSAFE tells the bundled unistr.h to provide a
function prototype for u8_mbtouc_unsafe. This prevents build failures
with future compilers which do not support implicit function
declarations.

Upstream gnulib has split the linebreak module into multiple parts; it
is hard to tell if it still has the same issue.

Submitted upstream: <https://github.com/tux4kids/t4kcommon/pull/16>

diff --git a/src/linebreak/linebreak.c b/src/linebreak/linebreak.c
index f9c88a15311aaf6b..0a40d376137b5479 100644
--- a/src/linebreak/linebreak.c
+++ b/src/linebreak/linebreak.c
@@ -35,6 +35,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 //#include "c-ctype.h"
 #include "ctype.h"
 #include "xsize.h"
+#define GNULIB_UNISTR_U8_MBTOUC_UNSAFE
 #include "unistr.h"
 #include "uniwidth.h"
 #include "uniwidth/cjk.h"