introduce ability to pass sqlite_omit_load_extension

sqlite_omit_load_extension is a go build tag which behaves much like its
C counterpart SQLITE_OMIT_LOAD_EXTENSION

Signed-off-by: Jessica Frazelle <acidburn@docker.com>

sqlite3_omit_load_extension.go

@@ -0,0 +1,19 @@
+// Copyright (C) 2014 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+// +build sqlite_omit_load_extension
+
+package sqlite3
+
+/*
+#cgo CFLAGS: -DSQLITE_OMIT_LOAD_EXTENSION
+*/
+import "C"
+import (
+	"errors"
+)
+
+func (c *SQLiteConn) loadExtensions(extensions []string) error {
+	return errors.New("Extensions have been disabled for static builds")
+}