We're already exporting the entry functions (eglGetPlatformDisplayEXT(), etc.).
Valid platform enums are defined by separate KHR_platform_* extensions.

Bug swiftshader:58

Change-Id: I1eb030f76cd800be9ecb37bad36dd004aceeb1af
Reviewed-on: https://swiftshader-review.googlesource.com/9953Reviewed-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <capn@google.com>