tcg: Add TCGMemOp

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-i386: Use TCGMemOp within qemu_ldst routines

Step one in the transition, with constants passed down from tcg_out_op.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-ppc: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-ppc64: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-mips: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-sparc: Use TCGMemOp within qemu_ldst routines

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Add qemu_ld_st_i32/64

Step two in the transition, adding the new ldst opcodes.  Keep the old
opcodes around until all backends support the new opcodes.

Signed-off-by: Richard Henderson <rth@twiddle.net>
exec: Add both big- and little-endian memory helpers

Step three in the transition: helpers not tied to the target
"default" endianness.  To be used when the guest uses a memory
operation with non-default endianness.

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