clean up php extensions definitions

Using a job-template I should have.

Change-Id: Ic281527db9b2751977be9aa46a410baaa6b89c15
PHP extensions jobs marked with hasContintPackages

Building a PHP extension requires 'phpize' which is provided by
'php5-dev'.  As such, mark jobs with label 'hasContintPackages'.

Updated jobs:

php-FastStringSearch-build
php-NativePreprocessor-build
php-luasandbox-build
php-wikidiff-build
php-wikidiff2-build
php-wmerrors-build

Change-Id: I695f3f88bd1bdbf975c4d111af6d630b01cdb55f