Changes to the IBM 386/486 and RapidCAD CPUs

- Disabled the 'is486' flag and moved them to 386 timings
- Disabled cache on startup, enable-able later
- RapidCAD fixes (permanently disable L1, correct EDX reset)

src/cpu_common/cpu.h

@@ -382,7 +382,8 @@ extern int	cpu_cyrix_alignment;	/*Cyrix 5x86/6x86 only has data misalignment
 					  penalties when crossing 8-byte boundaries*/
 
 extern int		is8086,	is286, is386, is486, is486sx, is486dx, is486sx2, is486dx2, isdx4;
-extern int      	isibmcpu;
+extern int      hascache;
+extern int      isibm486;
 extern int		is_rapidcad;
 extern int		hasfpu;
 #define CPU_FEATURE_RDTSC (1 << 0)