Fix Travis build errors.

src/backend/dbi/test/test-backend-dbi-basic.cpp

@@ -60,6 +60,7 @@ extern "C"
 
 #include <string>
 #include <vector>
+#include <algorithm>
 
 #include "test-dbi-stuff.h"
 #include "test-dbi-business-stuff.h"

src/backend/sql/gnc-account-sql.cpp

@@ -42,6 +42,10 @@ extern "C"
 #endif
 }
 
+#include <string>
+#include <vector>
+#include <algorithm>
+
 #include "gnc-sql-connection.hpp"
 #include "gnc-sql-backend.hpp"
 #include "gnc-sql-object-backend.hpp"

src/backend/sql/gnc-bill-term-sql.cpp

@@ -41,6 +41,10 @@ extern "C"
 #include "qof.h"
 }
 
+#include <string>
+#include <vector>
+#include <algorithm>
+
 #include "gnc-sql-connection.hpp"
 #include "gnc-sql-backend.hpp"
 #include "gnc-sql-object-backend.hpp"

src/backend/sql/gnc-tax-table-sql.cpp

@@ -40,6 +40,10 @@ extern "C"
 #include "gncTaxTableP.h"
 }
 
+#include <string>
+#include <vector>
+#include <algorithm>
+
 #include "gnc-sql-connection.hpp"
 #include "gnc-sql-backend.hpp"
 #include "gnc-sql-object-backend.hpp"