Use new macro QEMU_PACKED for packed structures

Most changes were made using these commands:

git grep -la '__attribute__((packed))'|xargs perl -pi -e 's/__attribute__\(\(packed\)\)/QEMU_PACKED/'
git grep -la '__attribute__ ((packed))'|xargs perl -pi -e 's/__attribute__ \(\(packed\)\)/QEMU_PACKED/'
git grep -la '__attribute__((__packed__))'|xargs perl -pi -e 's/__attribute__\(\(__packed__\)\)/QEMU_PACKED/'
git grep -la '__attribute__ ((__packed__))'|xargs perl -pi -e 's/__attribute__ \(\(__packed__\)\)/QEMU_PACKED/'
git grep -la '__attribute((packed))'|xargs perl -pi -e 's/__attribute\(\(packed\)\)/QEMU_PACKED/'

Whitespace in linux-user/syscall_defs.h was fixed manually
to avoid warnings from scripts/checkpatch.pl.

Manual changes were also applied to hw/pc.c.

I did not fix indentation with tabs in block/vvfat.c.
The patch will show 4 errors with scripts/checkpatch.pl.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

target-s390x/cpu.h

@@ -698,7 +698,7 @@ typedef struct LowCore
     /* align to the top of the prefix area */
 
     uint8_t         pad18[0x2000-0x1400];      /* 0x1400 */
-} __attribute__((packed)) LowCore;
+} QEMU_PACKED LowCore;
 
 /* STSI */
 #define STSI_LEVEL_MASK         0x00000000f0000000ULL