basic_string.h: Fix _S_local_capacity for large sizeof(_CharT).

2014-12-22  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/bits/basic_string.h: Fix _S_local_capacity for
	large sizeof(_CharT).

From-SVN: r219031

libstdc++-v3/ChangeLog

+2014-12-22  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/bits/basic_string.h: Fix _S_local_capacity for
+	large sizeof(_CharT).
+
 2014-12-22  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/37522

libstdc++-v3/include/bits/basic_string.h

@@ -114,7 +114,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       _Alloc_hider	_M_dataplus;
       size_type		_M_string_length;
 
-      enum { _S_local_capacity = 16 / sizeof(_CharT) - 1 };
+      enum { _S_local_capacity = 15 / sizeof(_CharT) };
 
       union
       {