php-memcached: fix legal info

LICENSE file refer to PHP license version 3.01. License header in all
source files refer to PHP license version 3.01 except source files for
fastlz library which is provided under MIT license and g_fmt.{c,h}
which has ISC-like license header.

Signed-off-by: Rahul Bedarkar <rahulbedarkar89@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>