Finish hooking up ClangIR code gen into the Clang control flow,
initializing enough that basic code gen is possible.
Add an almost empty `cir.func` op to the ClangIR dialect. Currently the
only property of the function is its name. Add the code necessary to
code gen a cir.func op.
Create essentially empty files
clang/lib/CIR/Dialect/IR/{CIRAttrs.cpp,CIRTypes.cpp}. These will be
filled in later as attributes and types are defined in the ClangIR
dialect.
(Part of upstreaming the ClangIR incubator project into LLVM.)
c695a32576