Put a 1-character unget buffer into cin.  This fixes http://llvm.org/bugs/show_bug.cgi?id=15867

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@181470 91177308-0d34-0410-b5e6-96231b3b80d8
Initialize codecvt explicitly with the C locale, which might not be 0.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@181534 91177308-0d34-0410-b5e6-96231b3b80d8