acl: refactor and clean up

Move all C code to c.go, switch to pkg-config, set up finalizer for acl.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

acl/acl.go

@@ -0,0 +1,19 @@
+// Package acl implements simple ACL manipulation via libacl.
+package acl
+
+type Perms []Perm
+
+func (ps Perms) String() string {
+	var s = []byte("---")
+	for _, p := range ps {
+		switch p {
+		case Read:
+			s[0] = 'r'
+		case Write:
+			s[1] = 'w'
+		case Execute:
+			s[2] = 'x'
+		}
+	}
+	return string(s)
+}