appveyor: use PHP 7.0.7 for build

appveyor.yml

@@ -8,7 +8,7 @@ environment:
     OUTDIR: Release
     CONFIGURE_EXTRA: --disable-zts
 
-  PHP_VERSION: 7.0.1
+  PHP_VERSION: 7.0.7
   PHP_SDK: c:\projects\php-sdk
 
 os: Windows Server 2012