layers: GH706, Allow GLSL shaders during validation
layers: GH706, Allow GLSL shaders during validation

Validation will now ignore shader shages created with GLSL when
using the NV_GLSL_SHADER extension.

Change-Id: Iaa4b284c6491a5be8d77f4616018a0cd05af8d18

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers