small changes in sendmsg.c regtest
* avoid a warning related to pointer types
* replace exit (0) by return 0 (might help backtraces on Darwin, suggestion by Rich Coe)



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13301 a5019735-40e9-0310-863c-91ae7b9d1cf9
Factorise some code from syswrap-amd64/arm/mips32/mips64-linux.c to syswrap-linux.c

Almost mechanical transformation, removes > 1000 SLOC.

Compiled and regtested on amd64/x86/mips32
Compiled and (somewhat) tested on mips64
Compiled on arm



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13302 a5019735-40e9-0310-863c-91ae7b9d1cf9