fifteen: Ship recompiled version of PHP.

According to http://forum.ipfire.org/index.php?topic=9668.msg63198#msg63198,
it is required to recompile PHP after the mysql alignment fixes.

diff --git a/config/rootfiles/core/fifteen/filelists/php b/config/rootfiles/core/fifteen/filelists/php
new file mode 120000 (symlink)
index 0000000..1ae48d7
--- /dev/null
+++ b/config/rootfiles/core/fifteen/filelists/php
@@ -0,0 +1 @@
+../../../common/php
\ No newline at end of file