Clear error state flags in binarystream::rewind().

This patch is taken from the downstream google-breakpad in Chromium OS
(https://gerrit.chromium.org/gerrit/#change,7797), which makes
binarystream::rewind() properly clear error state flags.

BUG=460
TEST=Tested in downstream google-breakpad in Chromium OS.
A=asharif@chromium.org
Review URL: http://breakpad.appspot.com/339001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@901 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/processor/binarystream.h

@@ -77,6 +77,9 @@ class binarystream {
   void rewind() {
     stream_.seekg (0, ios::beg);
     stream_.seekp (0, ios::beg);
+    // This is to clear all the error flags, since only the EOF flag is cleared
+    // with seekg().
+    stream_.clear();
   }
 
  private: