In preparation for adding more builtins, factor out the handling of
builtin function kinds into separate files.
Add checking for builtin function signatures. The mechanism used here is
intended to provide a lot of flexibility for declaring generic builtin
functions and pretty arbitrary constraints on the types of parameters of
builtin functions. For now, these constraints are checked when the
builtin function is declared. The hope is that this will suffice, but if
not, it should be straightforward to switch to doing some of the
checking on call and share logic between the checks.
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Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
Richard SmithandJon Ross-Perkins
