Enables mssql support (#383)

* Enables mssql support

Port of dlobs work in gogs.
Enables options in index.js
Enables MSSQL as a database option in go.
Sets ID to 0 on initial migration. Required for
MSSQL insert statements.

Signed-off-by: Beau Trepp <beautrepp@gmail.com>

* Vendors in denisenkom/go-mssqldb

Includes golang.org/x/crypto/md4
as this is required by go-msssqldb

Signed-off-by: Beau Trepp <beautrepp@gmail.com>

vendor/github.com/denisenkom/go-mssqldb/net.go

@@ -0,0 +1,99 @@
+package mssql
+
+import (
+	"fmt"
+	"net"
+	"time"
+)
+
+type timeoutConn struct {
+	c             net.Conn
+	timeout       time.Duration
+	buf           *tdsBuffer
+	packetPending bool
+	continueRead  bool
+}
+
+func NewTimeoutConn(conn net.Conn, timeout time.Duration) *timeoutConn {
+	return &timeoutConn{
+		c:       conn,
+		timeout: timeout,
+	}
+}
+
+func (c *timeoutConn) Read(b []byte) (n int, err error) {
+	if c.buf != nil {
+		if c.packetPending {
+			c.packetPending = false
+			err = c.buf.FinishPacket()
+			if err != nil {
+				err = fmt.Errorf("Cannot send handshake packet: %s", err.Error())
+				return
+			}
+			c.continueRead = false
+		}
+		if !c.continueRead {
+			var packet uint8
+			packet, err = c.buf.BeginRead()
+			if err != nil {
+				err = fmt.Errorf("Cannot read handshake packet: %s", err.Error())
+				return
+			}
+			if packet != packPrelogin {
+				err = fmt.Errorf("unexpected packet %d, expecting prelogin", packet)
+				return
+			}
+			c.continueRead = true
+		}
+		n, err = c.buf.Read(b)
+		return
+	}
+	err = c.c.SetDeadline(time.Now().Add(c.timeout))
+	if err != nil {
+		return
+	}
+	return c.c.Read(b)
+}
+
+func (c *timeoutConn) Write(b []byte) (n int, err error) {
+	if c.buf != nil {
+		if !c.packetPending {
+			c.buf.BeginPacket(packPrelogin)
+			c.packetPending = true
+		}
+		n, err = c.buf.Write(b)
+		if err != nil {
+			return
+		}
+		return
+	}
+	err = c.c.SetDeadline(time.Now().Add(c.timeout))
+	if err != nil {
+		return
+	}
+	return c.c.Write(b)
+}
+
+func (c timeoutConn) Close() error {
+	return c.c.Close()
+}
+
+func (c timeoutConn) LocalAddr() net.Addr {
+	return c.c.LocalAddr()
+}
+
+func (c timeoutConn) RemoteAddr() net.Addr {
+	return c.c.RemoteAddr()
+}
+
+func (c timeoutConn) SetDeadline(t time.Time) error {
+	panic("Not implemented")
+}
+
+func (c timeoutConn) SetReadDeadline(t time.Time) error {
+	panic("Not implemented")
+}
+
+func (c timeoutConn) SetWriteDeadline(t time.Time) error {
+	panic("Not implemented")
+}