Fixed incorrect parameters for memory deallocation

examples/winapi/winapi.q

@@ -1,10 +1,4 @@
-import mem
-
 main() {
-	text := mem.alloc(4)
+	text := "Hi!\0"
-	text[0] = 'H'
+	user32.MessageBoxA(0, text, text, 0x240040)
-	text[1] = 'i'
-	text[2] = '!'
-	user32.MessageBoxA(0, text, text, 0x00240040)
-	mem.free(text, 4)
 }

lib/mem/free.q

@@ -1,5 +1,5 @@
 import sys
 
 free(address Pointer, length Int) -> Int {
-	return sys.munmap(address, length)
+	return sys.munmap(address-8, length+8)
 }

tests/programs/memory-free.q

@@ -0,0 +1,7 @@
+import mem
+
+main() {
+	address := mem.alloc(1024)
+	err := mem.free(address, 1024)
+	assert err == 0
+}

tests/programs_test.go

@@ -59,6 +59,7 @@ var programs = []struct {
 	{"switch", "", "", 0},
 	{"loop", "", "", 0},
 	{"loop-lifetime", "", "", 0},
+	{"memory-free", "", "", 0},
 	{"out-of-memory", "", "", 0},
 	{"struct", "", "", 0},
 }