The pass which instruments checkers before
memory accesses (load/store).
This allows to handle invalid memory accesses.

The patch is related to issue:
https://discuss.tvm.ai/t/array-bounds-checking/944

* [RELAY] Finish alter op pass

* [RELAY] AlterOpLayout Pass

* fix broadcast operators

* fix broadcast operators

* fix broadcast operators

* Support concatenate

* address comments

* address comments

* add comments

* rebase

Remove redundant item `tvm.relay.sigmoid` from langref/relay_op.rst

tvm.Schedule ==> tvm.schedule.Schedule

* [Tutorial]NLP Sequence to sequence model for translation

* Review comments

* Review comments updated

* Implement C code generation with tests

* Code cleanup

* Implement C code generation with tests

* Code cleanup

* tabs to spaces

* make lint compliant

* update export_library and reserve unique C keywords

* move ReserveKeywordsAsUnique to codegen_c

* some documentation and code cleanup

* use tvm.contrib.util for tempdir in testcases

* Port densenet to Relay

* Invoke densenet test in __main()__

* Even the spacing in the IR text format tests

* Forgot to import densenet in init

* Correct reference to densenet in test