[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

Examples/php5/pointer/example.i

@@ -0,0 +1,30 @@
+/* File : example.i */
+%module example
+
+%{
+extern void add(double *, double *, double *);
+extern void sub(int *, int *, int *);
+extern int divide(int, int, int *);
+%}
+
+/* This example illustrates a couple of different techniques
+   for manipulating C pointers */
+
+%include phppointers.i
+/* First we'll use the pointer library */
+extern void add(double *REF, double *REF, double *REF);
+
+/* Next we'll use some typemaps */
+
+%include typemaps.i
+extern void sub(int *INPUT, int *INPUT, int *OUTPUT);
+
+/* Next we'll use typemaps and the %apply directive */
+
+//%apply int *OUTPUT { int *r };
+//extern int divide(int n, int d, int *r);
+
+
+
+
+