Fix the error message for when an erroneous HLSL constructor statement
is detected.
Prior to this change, such error messages would not show correct file
path and line number information.
Additionally, update test data to account for updated error messages.
Texture shadow mode must match the state of the sampler they are
combined with. This change does that, both for the AST and the
symbol table. Note that the texture cannot easily be *created*
the right way, because this may not be known at that time. Instead,
the texture is subsequently patched.
This cannot work if a single texture is used with both a shadow and
non-shadow sampler, so that case is detected and generates an error.
This is permitted by the HLSL language, however. See #1073 discussion.
Fixed one test source that was using a texture with both shadow and
non-shadow samplers.
