target/i386: convert bit test instructions to new decoder

target/i386: convert bit test instructions to new decoder

Code generation was rewritten; it reuses the same trick to use the
CC_OP_SAR values for cc_op, but it tries to use CC_OP_ADCX or CC_OP_ADCOX
instead of CC_OP_EFLAGS.  This is a tiny bit more efficient in the
common case where only CF is checked in the resulting flags.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>