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/charset.go

@@ -0,0 +1,113 @@
+package mssql
+
+type charsetMap struct {
+	sb [256]rune    // single byte runes, -1 for a double byte character lead byte
+	db map[int]rune // double byte runes
+}
+
+func collation2charset(col collation) *charsetMap {
+	// http://msdn.microsoft.com/en-us/library/ms144250.aspx
+	// http://msdn.microsoft.com/en-us/library/ms144250(v=sql.105).aspx
+	switch col.sortId {
+	case 30, 31, 32, 33, 34:
+		return cp437
+	case 40, 41, 42, 44, 49, 55, 56, 57, 58, 59, 60, 61:
+		return cp850
+	case 50, 51, 52, 53, 54, 71, 72, 73, 74, 75:
+		return cp1252
+	case 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96:
+		return cp1250
+	case 104, 105, 106, 107, 108:
+		return cp1251
+	case 112, 113, 114, 121, 124:
+		return cp1253
+	case 128, 129, 130:
+		return cp1254
+	case 136, 137, 138:
+		return cp1255
+	case 144, 145, 146:
+		return cp1256
+	case 152, 153, 154, 155, 156, 157, 158, 159, 160:
+		return cp1257
+	case 183, 184, 185, 186:
+		return cp1252
+	case 192, 193:
+		return cp932
+	case 194, 195:
+		return cp949
+	case 196, 197:
+		return cp950
+	case 198, 199:
+		return cp936
+	case 200:
+		return cp932
+	case 201:
+		return cp949
+	case 202:
+		return cp950
+	case 203:
+		return cp936
+	case 204, 205, 206:
+		return cp874
+	case 210, 211, 212, 213, 214, 215, 216, 217:
+		return cp1252
+	}
+	// http://technet.microsoft.com/en-us/library/aa176553(v=sql.80).aspx
+	switch col.getLcid() {
+	case 0x001e, 0x041e:
+		return cp874
+	case 0x0411, 0x10411:
+		return cp932
+	case 0x0804, 0x1004, 0x20804:
+		return cp936
+	case 0x0012, 0x0412:
+		return cp949
+	case 0x0404, 0x1404, 0x0c04, 0x7c04, 0x30404:
+		return cp950
+	case 0x041c, 0x041a, 0x0405, 0x040e, 0x104e, 0x0415, 0x0418, 0x041b, 0x0424, 0x1040e:
+		return cp1250
+	case 0x0423, 0x0402, 0x042f, 0x0419, 0x081a, 0x0c1a, 0x0422, 0x043f, 0x0444, 0x082c:
+		return cp1251
+	case 0x0408:
+		return cp1253
+	case 0x041f, 0x042c, 0x0443:
+		return cp1254
+	case 0x040d:
+		return cp1255
+	case 0x0401, 0x0801, 0xc01, 0x1001, 0x1401, 0x1801, 0x1c01, 0x2001, 0x2401, 0x2801, 0x2c01, 0x3001, 0x3401, 0x3801, 0x3c01, 0x4001, 0x0429, 0x0420:
+		return cp1256
+	case 0x0425, 0x0426, 0x0427, 0x0827:
+		return cp1257
+	case 0x042a:
+		return cp1258
+	case 0x0439, 0x045a, 0x0465:
+		return nil
+	}
+	return cp1252
+}
+
+func charset2utf8(col collation, s []byte) string {
+	cm := collation2charset(col)
+	if cm == nil {
+		return string(s)
+	}
+	buf := make([]rune, 0, len(s))
+	for i := 0; i < len(s); i++ {
+		ch := cm.sb[s[i]]
+		if ch == -1 {
+			if i+1 == len(s) {
+				ch = 0xfffd
+			} else {
+				n := int(s[i+1]) + (int(s[i]) << 8)
+				i++
+				var ok bool
+				ch, ok = cm.db[n]
+				if !ok {
+					ch = 0xfffd
+				}
+			}
+		}
+		buf = append(buf, ch)
+	}
+	return string(buf)
+}