Let the plugin know that a file is not being included in the link by
returning LDPS_NO_SYMS from get_symbols().
include/
* plugin-api.h (enum ld_plugin_tag): Add LDPT_GET_SYMBOLS_V3.
gold/
* plugin.h (Pluginobj::get_symbol_resolution_info): Add version
parameter.
* plugin.cc (get_symbols_v3): New function.
(Plugin::load): Add LDPT_GET_SYMBOLS_V3.
(Pluginobj::get_symbol_resolution_info): Return LDPS_NO_SYMS when using
new version.
