xgettext: In language Tcl, avoid a crash at surrogate character escapes.
* gettext-tools/src/x-tcl.c (accumulate_word): Warn when seeing a surrogate
character, instead of aborting.
* gettext-tools/tests/xgettext-tcl-5: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add it.
