X86: Implement the undocumented SALC instruction which sets AL to 0xFF if CF=1 and 0x00 otherwise.

--HG--
extra : convert_revision : 845d43c544e296d7595f54054906055a9f21ad9f

src/arch/x86/isa/decoder/one_byte_opcodes.isa

@@ -461,7 +461,7 @@
             }
             0x6: decode MODE_SUBMODE {
                 0x0: UD2();
-                default: WarnUnimpl::salc();
+                default: SALC(rAb);
             }
             0x7: XLAT();
         }

src/arch/x86/isa/insts/general_purpose/compare_and_test/set_byte_on_condition.py

@@ -54,6 +54,11 @@
 # Authors: Gabe Black
 
 microcode = '''
+def macroop SALC_R
+{
+    sbb reg, reg, reg, dataSize=1
+};
+
 def macroop SETZ_R
 {
     movi reg, reg, 1, flags=(CZF,)