[BZ #6471]
* sysdeps/unix/sysv/linux/shmat.c (shmat): Test for syscall errors
properly.
* sysdeps/unix/sysv/linux/sparc/getshmlba.c: New file.
* sysdeps/unix/sysv/linux/sparc/Makefile: Add getshmlba to
sysdep_routines when subdir is sysvipc.
* sysdeps/unix/sysv/linux/sparc/bits/shm.h (SHMLBA): Use new
__getshmlba helper.
