[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/ModStream.cpp b/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
index 9f035cf..0c2d2c3 100644
--- a/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
@@ -31,7 +31,7 @@
 ModStream::~ModStream() = default;
 
 Error ModStream::reload() {
-  StreamReader Reader(*Stream);
+  BinaryStreamReader Reader(*Stream);
 
   uint32_t SymbolSize = Mod.getSymbolDebugInfoByteSize();
   uint32_t C11Size = Mod.getLineInfoByteSize();
@@ -41,7 +41,7 @@
     return make_error<RawError>(raw_error_code::corrupt_file,
                                 "Module has both C11 and C13 line info");
 
-  ReadableStreamRef S;
+  BinaryStreamRef S;
 
   if (auto EC = Reader.readInteger(Signature, llvm::support::little))
     return EC;
@@ -53,7 +53,7 @@
   if (auto EC = Reader.readStreamRef(C13LinesSubstream, C13Size))
     return EC;
 
-  StreamReader LineReader(C13LinesSubstream);
+  BinaryStreamReader LineReader(C13LinesSubstream);
   if (auto EC = LineReader.readArray(LineInfo, LineReader.bytesRemaining()))
     return EC;