EGL: Add support for eglQueryDisplayAttribKHR and NV.

There are KHR, EXT, and NV versions of eglQueryDisplayAttrib, so add
support for all of them.

Define separate eglQueryDisplayAttribEXT, eglQueryDisplayAttribKHR, and
eglQueryDisplayAttribNV functions. They all call into the same common
function, with the only difference being the name passed to an error
callback.

When loading a vendor library, check for the vendor's
eglQueryDisplayAttrib using all three suffixes, and use whichever one is
available.
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