Feature/upgrade libjpeg (#1769)

* Upgrades dlib's included libjpeg to version 8d

* Overloads load_jpeg to read from memory buffer

* Removes "__inline__" define in jconfig, broke VC build

* Changes buffer size type to size_t

dlib/external/libjpeg/jversion.h

-/*
- * jversion.h
- *
- * Copyright (C) 1991-1998, Thomas G. Lane.
- * This file is part of the Independent JPEG Group's software.
- * For conditions of distribution and use, see the accompanying README file.
- *
- * This file contains software version identification.
- */
-
-
-#define JVERSION	"6b  27-Mar-1998"
-
-#define JCOPYRIGHT	"Copyright (C) 1998, Thomas G. Lane"
+/*
+ * jversion.h
+ *
+ * Copyright (C) 1991-2012, Thomas G. Lane, Guido Vollbeding.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains software version identification.
+ */
+
+
+#define JVERSION	"8d  15-Jan-2012"
+
+#define JCOPYRIGHT	"Copyright (C) 2012, Thomas G. Lane, Guido Vollbeding"