5.6.30+dfsg-0+deb8u1) is not available, but a newer one is (5.6.33+dfsg-0+deb8u1). We redirected you there.
/usr/share/php5/xsl/xsl.ini is in php5-xsl 5.6.33+dfsg-0+deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | ; configuration for php XSL module
; priority=20
extension=xsl.so
|