Simplify the handling of iterators in ObjectFile.

None of the object file formats reported error on iterator increment. In
retrospect, that is not too surprising: no object format stores symbols or
sections in a linked list or other structure that requires chasing pointers.
As a consequence, all error checking can be done on begin() and end().

This reduces the text segment of bin/llvm-readobj in my machine from 521233 to
518526 bytes.

llvm-svn: 200442
diff --git a/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp b/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
index 531595e..65c0ab7 100644
--- a/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
+++ b/llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp
@@ -151,11 +151,9 @@
     OwningPtr<DIContext> Context(DIContext::getDWARFContext(LoadedObject->getObjectFile()));
 
     // Use symbol info to iterate functions in the object.
-    error_code ec;
     for (object::symbol_iterator I = LoadedObject->begin_symbols(),
                                  E = LoadedObject->end_symbols();
-                          I != E && !ec;
-                          I.increment(ec)) {
+         I != E; ++I) {
       object::SymbolRef::Type SymType;
       if (I->getType(SymType)) continue;
       if (SymType == object::SymbolRef::ST_Function) {