R1:468aeaef0db7

Revert "Use phutil_split_lines() in Differential"

This reverts commit f6cb51562efd4f2e599d8ea69c5d5331d4de6d8d.

This has some bugs in normal diffs that I haven't immediately been able to figure out. I'll reapply it once I sort them out.

Auditors: vrana