Disable optimizeLoads().

Summary: Disable optimizeLoads(), which is generating bad VASM code for
AssertType.

Reviewed By: @jdelong

Differential Revision: D1711994
Fix up integration tests.

Summary: We now pass the list of changed files in a temporary file.

Reviewed By: @jwatzman

Differential Revision: D1707061

Signature: t1:1707061:1417478914:40b46940e89d2e9dd41a3347871064177b463058
Kill shell.ml entirely.

Summary: Replace by `Filename.quote`.

Reviewed By: @elgenie

Differential Revision: D1707066

Signature: t1:1707066:1417470648:cc8cd0bd93c80636770ab381d81a0c435e3fd7d5