[PDB] Make streams carry their own endianness.

Before the endianness was specified on each call to read
or write of the StreamReader / StreamWriter, but in practice
it's extremely rare for streams to have data encoded in
multiple different endiannesses, so we should optimize for the
99% use case.

This makes the code cleaner and more general, but otherwise
has NFC.

llvm-svn: 296415
diff --git a/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp b/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
index 0c2d2c3..df9ec81 100644
--- a/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/ModStream.cpp
@@ -43,7 +43,7 @@
 
   BinaryStreamRef S;
 
-  if (auto EC = Reader.readInteger(Signature, llvm::support::little))
+  if (auto EC = Reader.readInteger(Signature))
     return EC;
   if (auto EC = Reader.readArray(SymbolsSubstream, SymbolSize - 4))
     return EC;
@@ -58,7 +58,7 @@
     return EC;
 
   uint32_t GlobalRefsSize;
-  if (auto EC = Reader.readInteger(GlobalRefsSize, llvm::support::little))
+  if (auto EC = Reader.readInteger(GlobalRefsSize))
     return EC;
   if (auto EC = Reader.readStreamRef(GlobalRefsSubstream, GlobalRefsSize))
     return EC;