The required or desired behavior on out-of-bounds accesses depends on
the robustness feature, storage class, static analysis, debugging state
and paranoia level preference.

Specifically, this change:
- Omits bounds checks on local variable initialization.
- Omits bounds checks on modf() and frexp() output variables.
- Bounds checks on image read/write instead of using robustBufferAccess
  feature setting.
- Bounds checks on OpCopyMemory instead of using robustBufferAccess
  feature setting.

Bug: b/131224163
Change-Id: I199e73d42d9cce0645792dd1d876ea69d4ec3835
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/33988
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>