dump sc_cause, sc_status or sc_badvaddr.
* sysdeps/unix/sysv/linux/mips/bits/sigcontext.h: Rewrite. Update
structure definitions after DSP kernel changes.
* sysdeps/unix/sysv/linux/mips/sys/ucontext.h (mcontext_t): Update
after the same DSP changes.
* sysdeps/unix/sysv/linux/mips/sigcontextinfo.h: Port to n32/n64.
* sysdeps/unix/sysv/linux/mips/bits/sigcontext.h: New.
* sysdeps/unix/sysv/linux/mips/sys/ucontext.h: Port to n32/n64.
(mcontext_t): Make it match the 32-bit mips kernel in o32.
* sysdeps/unix/sysv/linux/mips/sys/user.h: Bring in constants from
the mips and mips64 headers.
(struct user): Port to n32/n64.