Drop the raw_ostream required buffer size to 1.

 - As best I can tell, we have eliminated all the code which used to require a
   larger buffer size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81912 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index 2cb3771..0a82cc1 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -84,8 +84,8 @@
 void raw_ostream::SetBufferAndMode(char *BufferStart, size_t Size, 
                                     BufferKind Mode) {
   assert(((Mode == Unbuffered && BufferStart == 0 && Size == 0) || 
-          (Mode != Unbuffered && BufferStart && Size >= 64)) &&
-         "stream must be unbuffered, or have >= 64 bytes of buffer");
+          (Mode != Unbuffered && BufferStart && Size)) &&
+         "stream must be unbuffered or have at least one byte");
   // Make sure the current buffer is free of content (we can't flush here; the
   // child buffer management logic will be in write_impl).
   assert(GetNumBytesInBuffer() == 0 && "Current buffer is non-empty!");