Fix multiple personalities support in parsers of ptrace,
rt_sigqueueinfo, rt_tgsigqueueinfo, rt_sigtimedwait and waitid syscalls
by converting printsiginfo_at into a mpersified printer.
* printsiginfo.c (siginfo_t): Mpersify.
(printsiginfo_at): Wrap function name into MPERS_PRINTER_DECL.
* defs.h (printsiginfo_at): Remove.
* signal.c (print_sigqueueinfo, sys_rt_sigtimedwait): Use mpersified
printsiginfo_at.
* process.c (sys_ptrace): Likewise.
* wait.c (sys_waitid): Likewise.