R1:26bca418289d

Improve setup process to detect 'open_basedir', 'date.timezone' and 'safe_mode'
problems

Summary: Detect more PHP misconfigurations in setup.
Test Plan: Broke my configuration, ran setup, it seemed to detect all the
problems and issue meaningful error messages.
Reviewed By: jungejason
Reviewers: hunterbridges, 10098, jungejason, tuomaspelkonen, aran
CC: aran, jungejason
Differential Revision: 717