* build-aux/announce-gen: Add two new options, both optional: --bootstrap-tools=TOOL_LIST a comma-separated list of tools, e.g., autoconf,automake,bison,gnulib --gnulib-snapshot-date=DATE if gnulib is in the bootstrap tool list, then report this as the snapshot date. If not specified, use the current date/time. If you specify a date here, be sure it's UTC.