[PDB] Partial resubmit of r296215, which improved PDB Stream Library.

This was reverted because it was breaking some builds, and
because of incorrect error code usage.  Since the CL was
large and contained many different things, I'm resubmitting
it in pieces.

This portion is NFC, and consists of:

1) Renaming classes to follow a consistent naming convention.
2) Fixing the const-ness of the interface methods.
3) Adding detailed doxygen comments.
4) Fixing a few instances of passing `const BinaryStream& X`.  These
   are now passed as `BinaryStreamRef X`.

llvm-svn: 296394
diff --git a/llvm/lib/DebugInfo/PDB/Native/SymbolStream.cpp b/llvm/lib/DebugInfo/PDB/Native/SymbolStream.cpp
index 3f0e07a..2d351b0 100644
--- a/llvm/lib/DebugInfo/PDB/Native/SymbolStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/SymbolStream.cpp
@@ -30,7 +30,7 @@
 SymbolStream::~SymbolStream() {}
 
 Error SymbolStream::reload() {
-  StreamReader Reader(*Stream);
+  BinaryStreamReader Reader(*Stream);
 
   if (auto EC = Reader.readArray(SymbolRecords, Stream->getLength()))
     return EC;