Revert "Added linking in bulitins to test_safeptr_builtin test, but for some reason name mangling does not to exact same result for builtin symbol names."

This reverts commit 05bd7344caeeb027a5f858cf592d4e572edc4069.
Unsafe builtin functions work again

pocl/library.bc now contains safe implementations (in their
transformed signature form). ClampPointers now properly maps from
unsafe implementations to the pointer range checking ones.