factorise sys_socketcall
sys_socketcall was duplicated in syswrap-{ppc64|ppc32|arm|mips32|s390x}-linux.c
=>
* Similarly for what was done for sys_ipc, factorise the code in syswrap-linux.c
* re-enabled PRE_MEM_READ for VKI_SYS_SENDMSG and VKI_SYS_RECVMSG 
  (PRE_MEM_READ calls were commented out around 2003, for what
   was supposed a glibc bug.
   The PRE_MEM_READ calls were already re-enabled in s390x)
* s390x also had some more checking to verify the addressibility of
  the args and fail the syscall with EFAULT if not addressable
  => same checks are now done for all platforms.

(tested on x86/amd64/mips32/s390x/ppc32/ppc64, 
 compiled for arm-android-emulator)



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13104 a5019735-40e9-0310-863c-91ae7b9d1cf9
9 files changed