Remove "typedef enum ..."

I noticed a few spots in GDB that use "typedef enum".  However, in C++
this isn't as useful, as the tag is automatically entered as a
typedef.  This patch removes most uses of "typedef enum" -- the
exceptions being in some nat-* code I can't compile, and
glibc_thread_db.h, which I think is more or less a copy of some C code
from elsewhere.

Tested by rebuilding.

gdb/python/py-event.h

@@ -45,13 +45,13 @@ extern int emit_exited_event (const LONGEST *exit_code, struct inferior *inf);
 /* For inferior function call events, discriminate whether event is
    before or after the call. */
 
-typedef enum
+enum inferior_call_kind
 {
   /* Before the call */
   INFERIOR_CALL_PRE,
   /* after the call */
   INFERIOR_CALL_POST,
-} inferior_call_kind;
+};
 
 extern int emit_inferior_call_event (inferior_call_kind kind,
 				     ptid_t thread, CORE_ADDR addr);