http://llvm.org/bugs/show_bug.cgi?id=9854.  Also created an emulated hexfloat literal for use in some of the tests. <sigh>  And cleaned up some harmless but irritating warnings in the tests.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@131318 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/iosfwd b/include/iosfwd
index 0e5c683..852d9e5 100644
--- a/include/iosfwd
+++ b/include/iosfwd
@@ -20,6 +20,7 @@
 template<class charT> struct char_traits;
 template<class T>     class allocator;
 
+class ios_base;
 template <class charT, class traits = char_traits<charT> > class basic_ios;
 
 template <class charT, class traits = char_traits<charT> > class basic_streambuf;