layers: Add param checks for CreateInstance/Device

Add parameter checks for vkCreateDevice and vkCreateInstance.
Includes a local fix for GitHub Vulkan-Docs issue #104 to
prevent false positives from being generated for the
pCreateInfo->pEnabledFeatures == NULL case.

Change-Id: I1f3642e7e18c8bfb32b0996b6e2e57a5f9d8e011
3 files changed