Update after gnulib changed.
* gettext-tools/src/read-csharp.c (execute_and_read_po_output): Does not need
write access to the elements of prog_argv.
* gettext-tools/src/read-java.c (execute_and_read_po_output): Likewise.
* gettext-tools/src/read-resources.c (execute_and_read_po_output): Likewise.
* gettext-tools/src/write-resources.c (execute_writing_input): Likewise.
* gettext-tools/src/urlget.c (execute_it): Likewise.
(fetch): Update variable types and remove casts to 'char *'.
* gettext-tools/src/msginit.c (project_id, project_id_version, get_user_email,
language_team_address, plural_forms): Likewise.
* gettext-tools/src/read-tcl.c (msgdomain_read_tcl): Likewise.
* gettext-tools/src/x-ruby.c (extract_ruby): Likewise.
* gettext-tools/src/msgexec.c (sub_argv): Change type to 'const char **'.
(main): Remove casts to 'char *'.
