Improved type safety for memory writes

tests/errors/TypeMismatch.q

@@ -2,6 +2,6 @@ main() {
 	writeToMemory(42)
 }
 
-writeToMemory(p *any) {
-	p[0] = 'A'
+writeToMemory(p *byte) {
+	[p] = 'A'
 }

tests/errors/TypeMismatch6.q

@@ -0,0 +1,6 @@
+import mem
+
+main() {
+	a := mem.alloc(1)
+	a[0] = int64(1)
+}