Refactor: Use function str_startswith.

Refactor: Use function str_startswith.

* libtextstyle/gnulib-local/lib/term-ostream.oo.c (should_enable_hyperlinks):
Use str_startswith.
* libtextstyle/gnulib-local/modules/term-ostream (Depends-on): Add
str_startswith.
* gettext-tools/src/cldr-plural.y (yylex): Use str_startswith.
* gettext-tools/src/format-java.c (message_format_parse, choice_format_parse):
Likewise.
* gettext-tools/src/msgl-check.c (plural_help, check_header_entry): Likewise.
* gettext-tools/src/read-catalog-abstract.c (parse_comment_filepos): Likewise.
* gettext-tools/src/read-csharp.c (msgdomain_read_csharp): Likewise.
* gettext-tools/src/write-csharp.c (msgdomain_write_csharp): Likewise.
* gettext-tools/src/x-perl.c (skip_pod): Likewise.
* autogen.sh (GNULIB_MODULES_TOOLS_FOR_SRC, GNULIB_MODULES_LIBGETTEXTPO): Add
str_startswith.