Remove var from list (bool, int, int64, string)

session/bool.go

@@ -23,3 +23,7 @@ func (s *Session) SetBool(name string, value bool) {
 		s.changed = true
 	}
 }
+
+func (s *Session) DelBool(name string) {
+	delete(s.varlist.Bool, name)
+}

session/int.go

@@ -23,3 +23,7 @@ func (s *Session) SetInt(name string, value int) {
 		s.changed = true
 	}
 }
+
+func (s *Session) DelInt(name string) {
+	delete(s.varlist.Int, name)
+}

session/int64.go

@@ -23,3 +23,7 @@ func (s *Session) SetInt64(name string, value int64) {
 		s.changed = true
 	}
 }
+
+func (s *Session) DelInt64(name string) {
+	delete(s.varlist.Int64, name)
+}

session/string.go

@@ -23,3 +23,7 @@ func (s *Session) SetString(name string, value string) {
 		s.changed = true
 	}
 }
+
+func (s *Session) DelString(name string) {
+	delete(s.varlist.String, name)
+}