nv50/ir/nir: implement images

nv50/ir/nir: implement images

v3: fix compiler warnings
v4: use loadFrom helper
v5: fix signed min/max
v6: set tex mask
    add support for indirect image access
    set cache mode
v7: make compatible with 884d27bcf688d36c3bbe01bceca525595add3b33
    rework the whole deref thing to prepare for bindless
v8: port to deref instructions
    don't require C++11 features
v9: implement MS images
    rebase on master (image modifiers)
    fix regressions due to variable src compnents
    replace '(*it).' with 'it->'
    convert to C++ style comments

Signed-off-by: Karol Herbst <kherbst@redhat.com>