[PHP] Add support for PHP7.

PHP5's C extension API has changed substantially so you need to use
-php7 to specify you want PHP7 compatible wrappers.
Fixes https://github.com/swig/swig/issues/571

Lib/php5/std_pair.i

@@ -0,0 +1,34 @@
+/* -----------------------------------------------------------------------------
+ * std_pair.i
+ *
+ * SWIG typemaps for std::pair
+ * ----------------------------------------------------------------------------- */
+
+%include <std_common.i>
+%include <exception.i>
+
+// ------------------------------------------------------------------------
+// std::pair
+// ------------------------------------------------------------------------
+
+%{
+#include <utility>
+%}
+
+namespace std {
+
+  template<class T, class U> struct pair {
+
+    pair();
+    pair(T first, U second);
+    pair(const pair& p);
+
+    template <class U1, class U2> pair(const pair<U1, U2> &p);
+
+    T first;
+    U second;
+  };
+
+  // add specializations here
+
+}