Some more tweaks to ENGINE code.

Previous changes permanently removed the commented-out old code for where
it was possible to create and use an ENGINE statically, and this code gets
rid of the ENGINE_FLAGS_MALLOCED flag that supported the distinction with
dynamically allocated ENGINEs. It also moves the area for ENGINE_FLAGS_***
values from engine_int.h to engine.h - because it should be possible to
declare ENGINEs just from declarations in exported headers.

crypto/engine/engine.h

@@ -83,6 +83,9 @@ extern "C" {
 #define ENGINE_METHOD_ALL		(unsigned int)0xFFFF
 #define ENGINE_METHOD_NONE		(unsigned int)0x0000
 
+/* ENGINE flags that can be set by ENGINE_set_flags(). */
+/* #define ENGINE_FLAGS_MALLOCED	0x0001 */ /* Not used */
+
 /* These flags are used to tell the ctrl function what should be done.
  * All command numbers are shared between all engines, even if some don't
  * make sense to some engines.  In such a case, they do nothing but return