qemu/compiler: Define QEMU_ARTIFICIAL

The combination of always_inline + artificial allows tiny inline
functions to be written that do not interfere with debugging.
In particular, gdb will not step into an artificial function.

The always_inline attribute was introduced in gcc 4.2,
and the artificial attribute was introduced in gcc 4.3.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Always enable TCGv type checking

Instead of using structures, which imply some amount of overhead
on certain ABIs, use pointer types.

This actually reduces the size of the binaries vs a NON-debug
build on ppc64 and x86_64, due to a reduction in the number of
sign-extension insns.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>