Support negation, parentheses. Always zero-extend registers for bugless memory operand usage

tests/bit-rounding.nct

@@ -1,2 +1,6 @@
 u32 x: 123;
-u33 y: 5;
+u33 y: 5;
+
+u3 *o = 5000;
+u3 z = *o;
+u3 p = *(o + z);

tests/if.nct

@@ -2,10 +2,11 @@ u16 x: 5;
 loop {
 	u16* y = 257;
 	u9 w = -4;
-	u4 z = 3 + *y;
+	u16 p = *y;
+	u4 z = p + 3;
 	u2 o = -w;
 	
 	if(x != 0) {
 		break;
 	}
-}
+}

tests/loopregalloc.nct

@@ -4,4 +4,6 @@ loop {
 	a = 3;
 	
 	u8 b = 1;
+	
+	u8 c = 2;
 }

tests/scoping.nct

@@ -1,5 +1,5 @@
 u8 a = 5;
-if(a) {
+if(a != 0) {
 	u8 a = 10; /* Should not cause scoping errors. */
 }
-u8 b = 15; /* `a` in the if statement scope should be free'd. */
+u8 b = 15; /* `a` in the if statement scope should be free'd. */