Clang (including trunk and many older versions) incorrectly marks static
local variables (__tag) hidden when -fvisibility-inlines-hidden is used.
This can lead to multiple instances of __tag when shares objects are used.

2018-07-20  Fangrui Song  <maskray@google.com>

	* include/bits/shared_ptr_base.h (_Sp_make_shared_tag::_S_ti): Use
	_GLIBCXX_VISIBILITY(default).

From-SVN: r262903