* resolve.cc (Symbol::override_base): Don't override st_type
from plugin placeholder symbols.
(Symbol_table::resolve): Likewise.
(Symbol_table::should_override): Don't complain about TLS mismatch
if the TO symbol is a plugin placeholder.
* testsuite/Makefile.am (plugin_test_tls): New test.
* testsuite/Makefile.in: Regenerate.
* testsuite/plugin_test_tls.sh: New test script.
* testsuite/two_file_test_2_tls.cc: New test source.
* testsuite/two_file_test_tls.cc: New test source.
