Fix 16-bit disp16 precedence bug in getecommon16o (#1066)

In C, == binds tighter than &, so 'm&7==6' parsed as 'm&(7==6)' = 'm&0' = always false. Disp16 was never fetched for mod==00,rm==110 16-bit addressing (GET_EW16_OFFS), leaving a wrong effective address and unadvanced EIP. Parenthesize as '(m&7)==6' to match getecommon16.

Author: As9xm

src/emu/modrm.h

@@ -108,7 +108,7 @@
             case 7: base =      R_BX; break;    \
         }                                       \
         switch((m>>6)&3) {                      \
-            case 0: if(m&7==6) base = F16S; break; \
+            case 0: if((m&7)==6) base = F16S; break; \
             case 1: base += F8S; break;         \
             case 2: base += F16S; break;        \
         }                                       \