stage2: implement more C pointer Sema and comptime ptr arith

test/behavior/pointers.zig

@@ -58,3 +58,38 @@ test "initialize const optional C pointer to null" {
     try expect(a == null);
     comptime try expect(a == null);
 }
+
+test "assigning integer to C pointer" {
+    var x: i32 = 0;
+    var ptr: [*c]u8 = 0;
+    var ptr2: [*c]u8 = x;
+    if (false) {
+        ptr;
+        ptr2;
+    }
+}
+
+test "C pointer comparison and arithmetic" {
+    const S = struct {
+        fn doTheTest() !void {
+            var ptr1: [*c]u32 = 0;
+            var ptr2 = ptr1 + 10;
+            try expect(ptr1 == 0);
+            try expect(ptr1 >= 0);
+            try expect(ptr1 <= 0);
+            // expect(ptr1 < 1);
+            // expect(ptr1 < one);
+            // expect(1 > ptr1);
+            // expect(one > ptr1);
+            try expect(ptr1 < ptr2);
+            try expect(ptr2 > ptr1);
+            try expect(ptr2 >= 40);
+            try expect(ptr2 == 40);
+            try expect(ptr2 <= 40);
+            ptr2 -= 10;
+            try expect(ptr1 == ptr2);
+        }
+    };
+    try S.doTheTest();
+    comptime try S.doTheTest();
+}