Add error checking and handling while loading captures

* Previously once we started loading a capture we'd blindly continue
  until we loaded it (and then it's assumed to be successful), or we
  crash.
* Now errors can be reported during serialisation and bubbled up to
  abort the file load process. The next steps are to add error checking
  in each function serialise before doing any replay calls to the API
  with potentially corrupt data, and on top of that catching API-only
  errors when the serialisation is (seemingly) fine, and propagating
  those in a reasonable way.
* We also harden the serialisation a bit so that if it reads an
  obviously invalid byte length for a buffer or array count, it won't
  continue. It's still not perfect as the sizes could still be large and
  invalid but within range, but it should catch the worst cases.

qrenderdoc/Windows/MainWindow.cpp

@@ -423,10 +423,18 @@ void MainWindow::LoadCapture(const QString &filename, bool temporary, bool local
     {
       ICaptureFile *file = RENDERDOC_OpenCaptureFile();
 
-      if(file->OpenFile(filename.toUtf8().data(), "rdc") != ReplayStatus::Succeeded)
+      ReplayStatus status = file->OpenFile(filename.toUtf8().data(), "rdc");
+
+      if(status != ReplayStatus::Succeeded)
       {
-        RDDialog::critical(NULL, tr("Error opening capture"),
-                           tr("Couldn't open file '%1'").arg(filename));
+        QString text = tr("Couldn't open file '%1'\n").arg(filename);
+        QString message = file->ErrorString();
+        if(message.isEmpty())
+          text += tr("%1").arg(ToQStr(status));
+        else
+          text += tr("%1: %2").arg(ToQStr(status)).arg(message);
+
+        RDDialog::critical(NULL, tr("Error opening capture"), text);
 
         file->Shutdown();
         return;
@@ -559,6 +567,8 @@ void MainWindow::LoadCapture(const QString &filename, bool temporary, bool local
         }
       }
 
+      statusText->setText(tr("Loading %1...").arg(origFilename));
+
       m_Ctx.LoadCapture(fileToLoad, origFilename, temporary, local);
     }
 
@@ -566,8 +576,6 @@ void MainWindow::LoadCapture(const QString &filename, bool temporary, bool local
     {
       m_Ctx.Config().LastCaptureFilePath = QFileInfo(filename).absolutePath();
     }
-
-    statusText->setText(tr("Loading %1...").arg(origFilename));
   }
 }
 
@@ -976,6 +984,7 @@ void MainWindow::setProgress(float val)
   if(val < 0.0f || val >= 1.0f)
   {
     statusProgress->setVisible(false);
+    statusText->setText(QString());
   }
   else
   {