mips-linux-user: Delete n32 and n64 signal stubs

Deleting these first makes the next patch much easier to read.
This doesn't cause any sort of compilation failure because we
have not yet enabled n32/n64 compilation.  This is dead code.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips-linux-user: Share o32 code for n32 and n64 signals

There are very few differences between the mips abis wrt
signal handling.  The major ones are the sigcontext struct
and the fact that n32/n64 don't have "traditional" signal
handlers, only "real-time" signal handlers.  All the rest
of the code can be shared.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips-linux-user: Enable mips64 and mipsn32 linux-user targets

At this point we can enable compilation, though things still don't work.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips-linux-user: Save and restore fpu and dsp from sigcontext

Probably not required by anything I'm ever planning to test,
but why not?  It's certainly easy to fill in these blanks...

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips-linux-user: Fix n32 and n64 syscalls

n32/n64 have different argument registers from o32.

In addition, use abi_long properly instead of the
host unsigned int for errno detection.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips64-linux-user: Enable 64-bit address mode and fpu

Signed-off-by: Richard Henderson <rth@twiddle.net>
mips64-linux-user: Use MIPS64R2-generic as default cpu.

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-mips: Fix check_cp1_64bitmode

COP1X refers to the availability of indexed memory operations,
not whether the FPU has 64-bit registers.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mipsn32-linux-user: Restrict address space to 31-bits.

Just like o32, n32 will fail if we don't respect the 31-bit address limit.

Signed-off-by: Richard Henderson <rth@twiddle.net>
mipsn32-linux-user: Configure the architecture properly

N32 is a 64-bit cpu with a 32-bit address space.  We have
existing cpp defines for this situation, but weren't using them.

This does mean that the linux-user/mipsn32 directory must be
merged with the linux-user/mips64 directory, and differences
must be resolved via ifdefs.

Signed-off-by: Richard Henderson <rth@twiddle.net>