Unify type spec by creating rs-spec-gen.

rs-spec-gen (slang_rs_spec_table.cpp) will help llvm-rs-cc to share
the RS spec it used across the other projects. This will makes code
cleaner and therefore easier to add new spec/synchronize the spec
between other project (e.g., libbcc and libRS).

This CL is the first part. It eliminated the needs of
slang_rs_export_element_support.inc and
slang_rs_export_type_support.inc.
9 files changed