Fix build issue with mysql.go

Including errmsg.h causes build problems on import.
So, punting on this for now by hardcoding the error code.

go/mysql/mysql.go

@@ -50,8 +50,9 @@ const (
 	// ErrOptionPreventsStatement is C.ER_OPTION_PREVENTS_STATEMENT
 	ErrOptionPreventsStatement = C.ER_OPTION_PREVENTS_STATEMENT
 
-	// ErrServerLost is C.CR_SERVER_LOST (2013)
-	ErrServerLost = C.CR_SERVER_LOST
+	// ErrServerLost is C.CR_SERVER_LOST.
+	// It's hard-coded for now because it causes problems on import.
+	ErrServerLost = 2013
 
 	// RedactedPassword is the password value used in redacted configs
 	RedactedPassword = "****"

go/mysql/vtmysql.h

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 #include <mysql.h>
-#include <errmsg.h>
 
 // This API provides convenient C wrapper functions for mysql client.