Fix basic_filebuf's internal buffer is shrinking when using with some codecvt.  http://llvm.org/bugs/show_bug.cgi?id=13602

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@162585 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed