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/tran.go

@@ -0,0 +1,99 @@
+// Transaction Manager requests
+// http://msdn.microsoft.com/en-us/library/dd339887.aspx
+package mssql
+
+import (
+	"encoding/binary"
+)
+
+const (
+	tmGetDtcAddr    = 0
+	tmPropagateXact = 1
+	tmBeginXact     = 5
+	tmPromoteXact   = 6
+	tmCommitXact    = 7
+	tmRollbackXact  = 8
+	tmSaveXact      = 9
+)
+
+func sendBeginXact(buf *tdsBuffer, headers []headerStruct, isolation uint8,
+	name string) (err error) {
+	buf.BeginPacket(packTransMgrReq)
+	writeAllHeaders(buf, headers)
+	var rqtype uint16 = tmBeginXact
+	err = binary.Write(buf, binary.LittleEndian, &rqtype)
+	if err != nil {
+		return
+	}
+	err = binary.Write(buf, binary.LittleEndian, &isolation)
+	if err != nil {
+		return
+	}
+	err = writeBVarChar(buf, name)
+	if err != nil {
+		return
+	}
+	return buf.FinishPacket()
+}
+
+const (
+	fBeginXact = 1
+)
+
+func sendCommitXact(buf *tdsBuffer, headers []headerStruct, name string, flags uint8, isolation uint8, newname string) error {
+	buf.BeginPacket(packTransMgrReq)
+	writeAllHeaders(buf, headers)
+	var rqtype uint16 = tmCommitXact
+	err := binary.Write(buf, binary.LittleEndian, &rqtype)
+	if err != nil {
+		return err
+	}
+	err = writeBVarChar(buf, name)
+	if err != nil {
+		return err
+	}
+	err = binary.Write(buf, binary.LittleEndian, &flags)
+	if err != nil {
+		return err
+	}
+	if flags&fBeginXact != 0 {
+		err = binary.Write(buf, binary.LittleEndian, &isolation)
+		if err != nil {
+			return err
+		}
+		err = writeBVarChar(buf, name)
+		if err != nil {
+			return err
+		}
+	}
+	return buf.FinishPacket()
+}
+
+func sendRollbackXact(buf *tdsBuffer, headers []headerStruct, name string, flags uint8, isolation uint8, newname string) error {
+	buf.BeginPacket(packTransMgrReq)
+	writeAllHeaders(buf, headers)
+	var rqtype uint16 = tmRollbackXact
+	err := binary.Write(buf, binary.LittleEndian, &rqtype)
+	if err != nil {
+		return err
+	}
+	err = writeBVarChar(buf, name)
+	if err != nil {
+		return err
+	}
+	err = binary.Write(buf, binary.LittleEndian, &flags)
+	if err != nil {
+		return err
+	}
+	if flags&fBeginXact != 0 {
+		err = binary.Write(buf, binary.LittleEndian, &isolation)
+		if err != nil {
+			return err
+		}
+		err = writeBVarChar(buf, name)
+		if err != nil {
+			return err
+		}
+	}
+	return buf.FinishPacket()
+}