target-i386: convert gen_compute_eflags_c to TCG

target-i386: convert gen_compute_eflags_c to TCG

Do the switch at translation time, converting the helper templates to
TCG opcodes.  In some cases CF can be computed with a single setcond,
though others it may require a little more work.

In the CC_OP_DYNAMIC case, compute the whole EFLAGS, same as for ZF/SF/PF.

Reviewed-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>