[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/variables/example.h

@@ -0,0 +1,34 @@
+/* File: example.h */
+
+typedef struct {
+  int x,y;
+} Point;
+
+/* Some global variable declarations */
+extern int              ivar;
+extern short            svar;
+extern long             lvar;
+extern unsigned int     uivar;
+extern unsigned short   usvar;
+extern unsigned long    ulvar;
+extern signed char      scvar;
+extern unsigned char    ucvar;
+extern char             cvar;
+extern float            fvar;
+extern double           dvar;
+extern char            *strvar;
+extern const char       cstrvar[];
+extern int             *iptrvar;
+extern char             name[5];
+
+extern Point           *ptptr;
+extern Point            pt;
+
+extern int  status;
+extern char path[256];
+
+extern void print_vars();
+extern int *new_int(int value);
+extern Point *new_Point(int x, int y);
+extern char *Point_print(Point *p);
+extern void pt_print();