Cleanup: move visibility/linkage attributes to the first declaration.

This change moves visibility attributes from out-of-class method
definitions to in-class declaration. This is needed for a switch to
attribute((internal_linkage)) (see http://reviews.llvm.org/D13925)
which can only appear on the first declaration.

This change does not touch istream/ostream/streambuf. They are
handled separately in http://reviews.llvm.org/D14409.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@252385 91177308-0d34-0410-b5e6-96231b3b80d8

include/regex

@@ -1048,6 +1048,7 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     int __regex_traits_value(char __ch, int __radix) const
         {return __regex_traits_value(static_cast<unsigned char>(__ch), __radix);}
+    _LIBCPP_INLINE_VISIBILITY
     int __regex_traits_value(wchar_t __ch, int __radix) const;
 };
 
@@ -1270,7 +1271,7 @@ regex_traits<_CharT>::__regex_traits_value(unsigned char __ch, int __radix)
 }
 
 template <class _CharT>
-inline _LIBCPP_INLINE_VISIBILITY
+inline
 int
 regex_traits<_CharT>::__regex_traits_value(wchar_t __ch, int __radix) const
 {