mediawiki::php: restore php5-igbinary; delete some unused files

I removed it and igbinary.ini before, not realizing that they were a dependency
for php5-memcached. I then restored igbinary.ini but not the package.

Change-Id: If649344368665ddb7340adc0400a13b2b9e8a6d9
Merge "mediawiki::php: restore php5-igbinary; delete some unused files" into production