[locale.categories] Promote static const data members to constexpr

See #4862 and [contents]/1.

Author: frederick-vs-ja

source/text.tex

@@ -480,7 +480,7 @@
     class id;
     // \ref{locale.category}, type \tcode{locale::category}
     using category = int;
-    static const category   // values assigned here are for exposition only
+    static constexpr category   // values assigned here are for exposition only
       none     = 0,
       collate  = 0x010, ctype    = 0x020,
       monetary = 0x040, numeric  = 0x080,
@@ -1724,7 +1724,7 @@
       const char* narrow(const char* low, const char* high, char dfault, char* to) const;
 
       static locale::id id;
-      static const size_t table_size = @\impdef@;
+      static constexpr size_t table_size = @\impdef@;
 
       const mask* table() const noexcept;
       static const mask* classic_table() noexcept;
@@ -4448,7 +4448,7 @@
       pattern      neg_format()    const;
 
       static locale::id id;
-      static const bool intl = International;
+      static constexpr bool intl = International;
 
     protected:
       ~moneypunct();