a.out: remove define-only CMAGIC, previously magic number

The last user was removed in 5.1 in
commit 08300f44 ("a.out: remove core dumping support")
but this is part of the UAPI headers, so this may want to either wait
until a.out is removed entirely, or be removed from the magic number doc
and silently remain in the header

A cursory glance on DCS didn't show any user code actually using this
value

Found with
grep MAGIC Documentation/process/magic-number.rst | while read -r mag _;
do git grep -wF "$mag"  | grep -ve '^Documentation.*magic-number.rst:' \
-qe ':#define '"$mag" || git grep -wF "$mag" | while IFS=: read -r f _;
do sed -i '/\b'"$mag"'\b/d' "$f"; done ; done
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Link: https://lore.kernel.org/r/9cbea062df7125ef43e2e0b2a67ede6ad1c5f27e.1663280877.git.nabijaczleweli@nabijaczleweli.xyzSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/process/magic-number.rst

@@ -69,7 +69,6 @@ Changelog::
 Magic Name            Number           Structure                File
 ===================== ================ ======================== ==========================================
 PG_MAGIC              'P'              pg_{read,write}_hdr      ``include/linux/pg.h``
-CMAGIC                0x0111           user                     ``include/linux/a.out.h``
 HDLC_MAGIC            0x239e           n_hdlc                   ``drivers/char/n_hdlc.c``
 APM_BIOS_MAGIC        0x4101           apm_user                 ``arch/x86/kernel/apm_32.c``
 FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``

Documentation/translations/it_IT/process/magic-number.rst

@@ -75,7 +75,6 @@ Registro dei cambiamenti::
 Nome magico           Numero           Struttura                File
 ===================== ================ ======================== ==========================================
 PG_MAGIC              'P'              pg_{read,write}_hdr      ``include/linux/pg.h``
-CMAGIC                0x0111           user                     ``include/linux/a.out.h``
 HDLC_MAGIC            0x239e           n_hdlc                   ``drivers/char/n_hdlc.c``
 APM_BIOS_MAGIC        0x4101           apm_user                 ``arch/x86/kernel/apm_32.c``
 FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``

Documentation/translations/zh_CN/process/magic-number.rst

@@ -58,7 +58,6 @@ Linux 魔术数
 魔术数名              数字             结构                     文件
 ===================== ================ ======================== ==========================================
 PG_MAGIC              'P'              pg_{read,write}_hdr      ``include/linux/pg.h``
-CMAGIC                0x0111           user                     ``include/linux/a.out.h``
 HDLC_MAGIC            0x239e           n_hdlc                   ``drivers/char/n_hdlc.c``
 APM_BIOS_MAGIC        0x4101           apm_user                 ``arch/x86/kernel/apm_32.c``
 FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``

Documentation/translations/zh_TW/process/magic-number.rst

@@ -61,7 +61,6 @@ Linux 魔術數
 魔術數名              數字             結構                     文件
 ===================== ================ ======================== ==========================================
 PG_MAGIC              'P'              pg_{read,write}_hdr      ``include/linux/pg.h``
-CMAGIC                0x0111           user                     ``include/linux/a.out.h``
 HDLC_MAGIC            0x239e           n_hdlc                   ``drivers/char/n_hdlc.c``
 APM_BIOS_MAGIC        0x4101           apm_user                 ``arch/x86/kernel/apm_32.c``
 FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``

include/uapi/linux/a.out.h

@@ -70,9 +70,6 @@ enum machine_type {
    The first page is unmapped to help trap NULL pointer references */
 #define QMAGIC 0314
 
-/* Code indicating core file.  */
-#define CMAGIC 0421
-
 #if !defined (N_BADMAG)
 #define N_BADMAG(x)	  (N_MAGIC(x) != OMAGIC		\
 			&& N_MAGIC(x) != NMAGIC		\