Add missing explicit instantiation for std::lower_bound template

Since commit r195676[1], it looks like
libstdc++-v3/src/c++11/hashtable_c++0x.cc is missing an explicit
instantiation for std::lower_bound.  This leads to libstdc++.so having
the symbol for that (missing) instantiation be undefined, thus
preventing executables from being linked with libstdc++.

The patchlet below seems to fixed the issue for me.

Boostrapped and tested on x86_64-unknown-linux-gnu.

[1]:

    commit bc36b44c7cb0e5e97ac807b8fb17507e0fb09008
    Author: fdumont <fdumont@138bc75d-0d04-0410-961f-82ee72b054a4>
    Date:   Fri Feb 1 20:44:41 2013 +0000

	2013-02-01  François Dumont  <fdumont@gcc.gnu.org>

	    * include/bits/hashtable_policy.h
	    (_Prime_rehash_policy::_M_next_bkt)
	    (_Prime_rehash_policy::_M_need_rehash): Move definition...
	    * src/c++11/hashtable_c++0x.cc: ... here.
	    * src/shared/hashtable-aux.cc: Remove c++config.h include.
	    * config/abi/gnu.ver (GLIBCXX_3.4.18): Export _Prime_rehash_policy
	    symbols.

	git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@195676 138bc75d-0d04-0410-961f-82ee72b054a4

libstdc++-v3/ChangeLog

	* libstdc++-v3/src/c++11/hashtable_c++0x.cc (namespace std): Add
	missing instantiation for std::lower_bound template.

From-SVN: r195783