string_view: Make the literal operators constexpr like the ctors they call.

2014-07-25  Ed Smith-Rowland  <3dw4rd@verizon.net>

	* include/experimental/string_view: Make the literal operators
	constexpr like the ctors they call.

From-SVN: r213037

libstdc++-v3/ChangeLog

+2014-07-25  Ed Smith-Rowland  <3dw4rd@verizon.net>
+
+	* include/experimental/string_view: Make the literal operators
+	constexpr like the ctors they call.
+
 2014-07-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* config/abi/post/x86_64-linux-gnu/x32/baseline_symbols.txt: Update.

libstdc++-v3/include/experimental/string_view

@@ -664,22 +664,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   inline namespace string_view_literals
   {
 
-    inline basic_string_view<char>
+    inline constexpr basic_string_view<char>
     operator""sv(const char* __str, size_t __len)
     { return basic_string_view<char>{__str, __len}; }
 
 #ifdef _GLIBCXX_USE_WCHAR_T
-    inline basic_string_view<wchar_t>
+    inline constexpr basic_string_view<wchar_t>
     operator""sv(const wchar_t* __str, size_t __len)
     { return basic_string_view<wchar_t>{__str, __len}; }
 #endif
 
 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
-    inline basic_string_view<char16_t>
+    inline constexpr basic_string_view<char16_t>
     operator""sv(const char16_t* __str, size_t __len)
     { return basic_string_view<char16_t>{__str, __len}; }
 
-    inline basic_string_view<char32_t>
+    inline constexpr basic_string_view<char32_t>
     operator""sv(const char32_t* __str, size_t __len)
     { return basic_string_view<char32_t>{__str, __len}; }
 #endif