[libc++] Fix parsing <string> in C++03.

Specifically, add a space between >> when closing templates.

Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 313d89724ce3ccf66c1c51849903e1e6d184dd85
diff --git a/include/string b/include/string
index a63c3e1..2556301 100644
--- a/include/string
+++ b/include/string
@@ -813,7 +813,7 @@
     basic_string(basic_string&& __str, const allocator_type& __a);
 #endif  // _LIBCPP_CXX03_LANG
 
-    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t>>
+    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t> >
     _LIBCPP_INLINE_VISIBILITY
     basic_string(const _CharT* __s) : __r_(__default_init_tag(), __default_init_tag()) {
       _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
@@ -823,7 +823,7 @@
 #   endif
     }
 
-    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t>>
+    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t> >
         _LIBCPP_INLINE_VISIBILITY
         basic_string(const _CharT* __s, const _Allocator& __a);
 
@@ -834,7 +834,7 @@
     _LIBCPP_INLINE_VISIBILITY
     basic_string(size_type __n, _CharT __c);
 
-    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t>>
+    template <class = _EnableIf<__is_allocator<_Allocator>::value, nullptr_t> >
         _LIBCPP_INLINE_VISIBILITY
         basic_string(size_type __n, _CharT __c, const _Allocator& __a);
 
@@ -858,10 +858,10 @@
         _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         explicit basic_string(const _Tp& __t, const allocator_type& __a);
 
-    template<class _InputIterator, class = _EnableIf<__is_cpp17_input_iterator<_InputIterator>::value>>
+    template<class _InputIterator, class = _EnableIf<__is_cpp17_input_iterator<_InputIterator>::value> >
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last);
-    template<class _InputIterator, class = _EnableIf<__is_cpp17_input_iterator<_InputIterator>::value>>
+    template<class _InputIterator, class = _EnableIf<__is_cpp17_input_iterator<_InputIterator>::value> >
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
 #ifndef _LIBCPP_CXX03_LANG