Expanded vec128 and VectorSub

Added double precision (f64) values to the vec128 structure
Added cases for all formats of data for vector subtraction in the
Value::VectorSub function

NOTE: Unsure what the saturate function is for however maintained
original functionality

src/xenia/base/vec128.h

@@ -90,7 +90,8 @@ typedef struct alignas(16) vec128_s {
       uint32_t uz;
       uint32_t uw;
     };
-    float f32[4];
+	float f32[4];
+	double f64[2];
     int8_t i8[16];
     uint8_t u8[16];
     int16_t i16[8];