sys/ptrace.h: remove obsolete Linux PTRACE_SEIZE_DEVEL constant

Remove enum __ptrace_flags along with the only constant it contains,
PTRACE_SEIZE_DEVEL, from Linux's sys/ptrace.h files.

Following GNU C library commit:
60e2846e2633a990bdf474004a373bde54c0bc5f

libc/sysdeps/linux/common/sys/ptrace.h

@@ -148,13 +148,6 @@ enum __ptrace_request
   PTRACE_LISTEN = 0x4208
 };
 
-
-/* Flag for PTRACE_LISTEN.  */
-enum __ptrace_flags
-{
-  PTRACE_SEIZE_DEVEL = 0x80000000
-};
-
 /* Options set using PTRACE_SETOPTIONS.  */
 enum __ptrace_setoptions
 {

libc/sysdeps/linux/powerpc/sys/ptrace.h

@@ -123,13 +123,6 @@ enum __ptrace_request
 #define PTRACE_PEEKSIGINFO PTRACE_PEEKSIGINFO
 };
 
-
-/* Flag for PTRACE_LISTEN.  */
-enum __ptrace_flags
-{
-  PTRACE_SEIZE_DEVEL = 0x80000000
-};
-
 /* Options set using PTRACE_SETOPTIONS.  */
 enum __ptrace_setoptions
 {

libc/sysdeps/linux/sparc/sys/ptrace.h

@@ -171,13 +171,6 @@ enum __ptrace_request
 #define PTRACE_PEEKSIGINFO PTRACE_PEEKSIGINFO
 };
 
-
-/* Flag for PTRACE_LISTEN.  */
-enum __ptrace_flags
-{
-  PTRACE_SEIZE_DEVEL = 0x80000000
-};
-
 /* Options set using PTRACE_SETOPTIONS.  */
 enum __ptrace_setoptions
 {

libc/sysdeps/linux/sparc64/sys/ptrace.h

@@ -171,13 +171,6 @@ enum __ptrace_request
 #define PTRACE_PEEKSIGINFO PTRACE_PEEKSIGINFO
 };
 
-
-/* Flag for PTRACE_LISTEN.  */
-enum __ptrace_flags
-{
-  PTRACE_SEIZE_DEVEL = 0x80000000
-};
-
 /* Options set using PTRACE_SETOPTIONS.  */
 enum __ptrace_setoptions
 {