xgettext: In language Tcl, avoid stack overflow.
* gettext-tools/src/x-tcl.c: Include error-progname.h.
(MAX_NESTING_DEPTH): New macro.
(bracket_nesting_depth, brace_nesting_depth): New variables.
(accumulate_word, read_word): Increase and check bracket_nesting_depth or
brace_nesting_depth before calling read_command_list recursively.
(extract_tcl): Initialize bracket_nesting_depth and brace_nesting_depth.
* gettext-tools/tests/xgettext-tcl-stackovfl-1: New file.
* gettext-tools/tests/xgettext-tcl-stackovfl-2: New file.
* gettext-tools/tests/xgettext-tcl-stackovfl-3: New file.
* gettext-tools/tests/xgettext-tcl-stackovfl-4: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add them.
