Install APC on Ubuntu trusty

Trusty does not have APC preinstalled (see
travis-ci/travis-ci#5618,
travis-ci/travis-ci#6853) so we need to
install it manually using PECL. `yes ''` allows to skip prompts and fill
it with default values.

tests/data/travis/apc-setup.sh

@@ -1,8 +1,9 @@
 #!/bin/sh -e
 
 if [ "$(expr "$TRAVIS_PHP_VERSION" "<" "5.5")" -eq 1 ]; then
-	echo "extension = apc.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
+	yes '' | pecl install apc
+	#echo "extension = apc.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
 	echo "apc.enable_cli = 1" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
 else
 	echo "Not installing APC as it is not available in PHP 5.5 anymore."
-fi
+fi