In x86: Fixed backward compatibility with C90 (#1969)

* In x86: fixed backward compatibility with C90

* Refact: define variables as empty, do calculations only after the check passed

* Removed extra spaces

MCRegisterInfo.c

@@ -133,13 +133,16 @@ const MCRegisterClass* MCRegisterInfo_getRegClass(const MCRegisterInfo *RI, unsi
 
 bool MCRegisterClass_contains(const MCRegisterClass *c, unsigned Reg)
 {
+	unsigned InByte = 0;
+	unsigned Byte = 0;
+
 	// Make sure that MCRegisterInfo_getRegClass didn't return 0
 	// (for calls to GETREGCLASS_CONTAIN0)
 	if(!c)
 		return false;
 
-	unsigned InByte = Reg % 8;
-	unsigned Byte = Reg / 8;
+	InByte = Reg % 8;
+	Byte = Reg / 8;
 
 	if (Byte >= c->RegSetSize)
 		return false;